Quantum Computing Modalities: Acoustic (Phononic) Quantum Systems

Marin Ivezic June 23, 2023

37 minutes read

(For other quantum computing modalities and architectures, see Taxonomy of Quantum Computing: Modalities & Architectures)

(Updated in Sep 2025 with the publication of “Acoustic phonon phase gates with number-resolving phonon detection”)

What It Is

Quantum acoustic quantum computing refers to using quantized mechanical vibrations – phonons – to store and process quantum information. Instead of relying on photons (particles of light) or electronic states of atoms, this modality leverages units of sound (vibrations in solid materials) as information carriers.

In practice, this is implemented with tiny mechanical resonators or acoustic wave devices on a chip. These devices can trap or guide phonons at microwave frequencies (billions of vibrations per second), and when cooled to extremely low temperatures they behave quantum mechanically (with energy in discrete quanta). A phonon mode can thus act as a quantum oscillator much like an electromagnetic cavity mode or a qubit memory element.

Crucially, phonons can interact strongly with other quantum systems (like superconducting qubits or defects in solids) via piezoelectric or stress coupling, allowing quantum information to be exchanged between stationary qubits and acoustic modes.

Using sound in quantum computing is conceptually similar to using light, but phonons have distinct advantages. Because sound travels much slower than light in a solid (~100,000× slower), acoustic wavelengths at GHz frequencies are much shorter than electromagnetic wavelengths, enabling compact on-chip resonators and delay lines. Phonons can be tightly confined in solid structures (like microfabricated acoustic cavities or waveguides) and do not radiate into free space as easily as photons. In fact, isolated acoustic resonators can have extremely long coherence times – in the right materials, phonon excitations can persist for milliseconds or even seconds. This is because photons can leak out (emit into vacuum or other radiation modes), whereas phonons, being vibrations in a solid, mostly stay contained unless something absorbs them.

These properties make phononic systems intriguing as quantum memories (storing qubit states for long durations) and as a potential platform for scalable quantum processors that integrate many resonators on a chip.

In summary, the quantum acoustic modality uses engineered mechanical vibrations as qubits or qubit-carrying modes. It merges techniques from quantum optomechanics (which pioneered control of mechanical oscillators at the quantum level) with those of circuit quantum electrodynamics. By coupling phonons to conventional qubits (e.g. superconducting circuits or spin qubits), one can control and read out the phonon states. Alternatively, phonons can themselves transfer quantum states between distant nodes (acting as “sound wave qubits” traveling through acoustic waveguides). The result is a hybrid approach: solid-state “sound” quanta facilitate quantum logic operations and communication in a way that is analogous to photonic systems, but with the benefit of strong on-chip interactions and potentially longer storage times.

Key Academic Papers

Research in quantum acoustics is relatively young, but it has been driven by a series of groundbreaking theoretical proposals and experiments starting in the early 2000s. Below are some of the most influential papers that chart the evolution of this modality from concept to practical demonstrations:

O’Connell et al. (2010) – “Quantum ground state and single-phonon control of a mechanical resonator”. This landmark Nature paper from 2010 was the first to demonstrate quantum control of a macroscopic mechanical oscillator. O’Connell and colleagues cooled a nanomechanical resonator to its quantum ground state and, using a superconducting qubit as a quantum sensor, swapped a single quantum of energy (a single phonon) between the qubit and the resonator. This experiment showed that a mechanical mode (a tiny “drum”) could be prepared in a definite quantum state (the 0- or 1-phonon Fock state) and measured without ambiguity. It was a pivotal proof that phonons in a solid device can obey quantum mechanics much like photons in a cavity, launching the field of quantum acoustics in the context of information processing.
Gustafsson et al. (2014) – “Propagating phonons coupled to an artificial atom”. Published in Science, this paper by Gustafsson et al. was the first to interface a superconducting qubit with a surface acoustic wave (SAW) resonator. The team demonstrated a chip where a transmon qubit was coupled to a SAW cavity and could emit or absorb single traveling phonons – essentially showing a quantum transistor for sound. The experiment can be seen as creating a “quantum acoustic” analog of cavity QED, sometimes dubbed circuit quantum acoustodynamics (cQAD). It proved that a qubit can exchange excitations with a phonon mode in a surface acoustic wave, and even send phonons into an acoustic transmission line. This opened the door to using traveling phonons as “flying qubits” and demonstrated basic components like acoustic beam splitters and mirrors at the quantum level.
Chu et al. (2017) – “Quantum acoustics with superconducting qubits”. This Science paper by Chu et al. showed a breakthrough in using bulk acoustic wave resonators. They coupled a transmon qubit to a high-overtone bulk acoustic wave resonator (HBAR) – essentially a piezoelectric sapphire device supporting many acoustic modes in the GHz range. Importantly, they achieved the strong coupling regime between the qubit and phonons, and observed long-lived phonon modes with coherence times >10 µs. By tuning the qubit into resonance with different acoustic modes, they saw clear vacuum Rabi splittings (qubit-phonon energy swaps) for multiple phonon modes. This experiment demonstrated that bulk acoustic resonators can serve as high-quality quantum memories (with phonon lifetimes comparable to or exceeding those of 3D microwave cavities). Chu et al. highlighted that because sound’s speed is low, phonons can be confined in a small volume with very high quality factor – a key advantage for storing quantum information.
Satzinger et al. (2018) – “Quantum control of surface acoustic-wave phonons”. In this Nature paper, researchers from U.C. Santa Barbara (including K. Satzinger and A. Cleland) took SAW-based quantum acoustics further by achieving full quantum tomography of a phonon state. They coupled a transmon to a SAW cavity and were able to generate single-phonon Fock states and even superpositions, then read out the phonon state by mapping it back onto the qubit. This was essentially a phononic analog of quantum optics experiments, verifying that the mechanical resonator could be prepared in a single-phonon state and measured with high fidelity. The work showed that piezoelectric SAW resonators can be manipulated at the single-phonon level just like optical cavities with single photons, firmly establishing the toolbox for quantum acoustic state control.
Chu et al. (2018) – “Creation and control of multi-phonon Fock states in a bulk acoustic-wave resonator”. Published back-to-back with the above (Nature 563, 2018), this paper (by the Yale group) demonstrated that one can not only control 0 or 1 phonon, but also create higher phonon number states (like 2, 3, … phonons) in an acoustic resonator. By sequentially swapping excitations from a qubit into the HBAR, they prepared and verified Fock states up to n=15 in the mechanical resonator. They also observed that each additional phonon causes a measurable shift in the qubit’s frequency (due to the strong coupling), allowing them to count phonons nondestructively by monitoring the qubit. This pair of 2018 papers (Satzinger and Chu) represented a major milestone: quantum acoustic systems were no longer limited to single quanta, but could manipulate complex quantum states of motion.
Bienfait et al. (2019) – “Phonon-mediated quantum state transfer and remote qubit entanglement”. This Science paper by Bienfait et al. showed that itinerant phonons can serve as a communication channel between distant qubits. They used a SAW transmission line to entangle two superconducting qubits via phonons. Each qubit was connected to an acoustic transducer, and by emitting a single phonon from one qubit and catching it at the other, the team achieved entanglement between the spatially separated qubits (creating a two-qubit Bell state linked by a traveling phonon). This was a remarkable proof-of-principle that “sound” can distribute quantum information much like photons in optical fibers. It established phonons as viable carriers for quantum communication on chip, analogous to how photons link nodes in quantum networks.
Dumur et al. (2021) – “Quantum communication with itinerant surface acoustic wave phonons”. In this open-access npj Quantum Information article, Dumur, Cleland and collaborators further developed the phonon-based networking concept. They demonstrated a single-phonon quantum link between two qubit nodes, using shaped microwave acoustic pulses in a 2-mm-long SAW waveguide. They transferred quantum states and even performed a rudimentary phonon-mediated logic operation between the nodes. This work highlighted both the potential and challenges of using phonons to connect quantum modules. It showed high-fidelity state transfer and entanglement using phonons traveling in a chip-scale acoustic waveguide, firmly establishing the acoustic analog of a quantum network bus.
Qiao et al. (2023) – “Splitting phonons: building a platform for linear mechanical quantum computing”. Appearing in Science, this paper by Qiao et al. (Cleland’s group at UChicago) demonstrated a phononic beam-splitter and interferometer for the first time. They showed that two phonons interfering at a mechanical beam splitter exhibit the quantum Hong-Ou-Mandel effect (two-phonon interference) – analogous to photons in linear optical quantum computing. By “splitting” phonons coherently, they built an acoustic Mach-Zehnder interferometer entirely on-chip. This set the stage for linear acoustic quantum computing, where phonons play the role that photons do in optical systems. The phrase “phonons are equivalent to photons” in the quantum sense was strongly supported by these results, suggesting that techniques from photonic quantum computing (like boson sampling or one-way computing with linear optics) could be ported to a solid-state acoustic platform.
Qiao et al. (2025) – “Acoustic phonon phase gates with number-resolving phonon detection”. Published in Nature Physics in 2025, this is a seminal achievement that brings deterministic quantum logic to the acoustic domain. The UChicago team showed that by scattering an itinerant phonon off a superconducting qubit, they could implement a controllable phase gate on the phonon state. In essence, the qubit acts as a nonlinear element that imparts a π-phase shift to a phonon conditioned on the qubit’s state – or equivalently, the phonon’s presence shifts the qubit, yielding a controlled phase flip. They combined this with a novel number-resolving phonon detector (using a qutrit level of the qubit to distinguish 0, 1, or 2 phonons) to demonstrate interference of one- and two-phonon states with full deterministic control. This is the first realization of a two-phonon quantum gate, showing that phonons can be used not just passively (like in linear optics) but actively for quantum computing. The authors note that this deterministic phonon control removes the inherent randomness that plagues photonic approaches, a potential “major advantage” for scaling up quantum processors.

(Many other important works exist, such as demonstrations of nanomechanical qubit memory with ultra-long lifetimes, multi-phonon entanglement between two separate mechanical resonators, and theoretical architectures for phononic quantum networks. However, the above papers represent the key milestones illustrating the emergence of quantum acoustics as a distinct modality.)

How It Works

At the heart of quantum acoustic computing is the coupling between phonons and conventional quantum systems. There are a few primary implementations, or “platforms,” under this modality:

Hybrid superconducting-acoustic systems

In this approach, a superconducting qubit (typically a transmon) is fabricated on a chip alongside an acoustic resonator. The resonator might be a SAW cavity formed by interdigitated transducers and acoustic mirrors, or a bulk acoustic cavity (HBAR) where a piezoelectric film on a substrate supports standing sound waves.

The qubit’s electric field interacts with the piezoelectric material, so an excitation in the qubit can generate a stress in the crystal – i.e. launch a phonon – and vice versa. This is analogous to how a qubit might exchange a photon with a microwave cavity in circuit QED. By tuning the qubit into resonance with a particular acoustic mode, one achieves a vacuum Rabi swap: the qubit excitation is converted into a single phonon in the resonator.

Fast control pulses allow coherent swaps, creating superposition states delocalized between the qubit and the phonon. The Hamiltonian is essentially a Jaynes-Cummings interaction, with coupling rates $$g$$ on the order of hundreds of kHz to a few MHz in experiments. If $$g$$ exceeds the decay rates, the system is in the strong coupling regime, enabling multiple coherent oscillations of energy between qubit and phonon before dissipation occurs.

The qubit can thus act as a quantum controller for the phonon: preparing it in a desired Fock state, performing logical operations (e.g. phase shifts via conditional frequency shifts), and measuring it by mapping the phonon state back to the qubit readout.

Surface acoustic wave (SAW) devices

SAWs are vibrations confined to the surface of a substrate. They are generated and detected by interdigitated electrodes that convert electrical signals to surface ripples. In quantum acoustic setups, SAW resonators can store phonons (by reflecting them between mirrors) or guide phonons as traveling waves between components.

One important use of SAWs is to create delay lines or “acoustic quantum channels.” Because the speed of sound is low, a SAW traveling across a chip might take microseconds to go from one end to the other, effectively serving as a delay that can interface with fast electronics or other qubits. Researchers have used this to create on-demand single phonon sources and detectors separated by millimeter-scale distances. For example, one qubit can emit a phonon into a SAW waveguide; a second qubit, located some distance away, is timed to absorb the phonon, entangling the two qubits. SAW devices thus enable quantum signal processing akin to optical fiber links, but on a chip.

They also allow creation of acoustic interferometers: using beam splitters (coupled acoustic channels) and phase shifters (e.g. by tuning qubit interactions or using interference in multi-path structures), one can interfere phonon paths just like optical paths. In the recent acoustic Mach-Zehnder experiments, for instance, two transmons acted as controllable sources that injected phonons into an acoustic circuit containing a beam splitter; the resulting interference at the outputs was observed via the qubits catching the phonons. Such setups realize mechanical versions of well-known quantum optical setups.

Nanomechanical and optomechanical resonators

Another class of platforms involves miniature oscillators (like nanobeams or membranes) coupled to qubits or optical cavities. In these systems, vibrations of a tiny mechanical element (often at MHz-to-GHz frequencies) interact either via strain (if coupled to a qubit) or via radiation pressure (if coupled to light in a cavity). Optomechanical devices, for example, can entangle phonons with photons and have been used to create non-classical phonon states.

While optomechanics is typically discussed in the context of sensing or transduction, it contributes to the quantum acoustic modality by providing ultra-coherent mechanical modes. A notable achievement was the 2020 result by MacCabe et al.: a nano-acoustic phononic crystal resonator with a lifetime exceeding 1 second at 5 GHz. Such a mechanical mode could store quantum information orders of magnitude longer than most qubits, making it a tantalizing quantum memory if it can be interfaced with qubits.

The interface challenge is active research: schemes exist to couple mechanical modes to superconducting circuits (via piezoelectric or magnetic coupling) and even to spin qubits like NV centers (via strain coupling). These hybrid approaches aim to leverage the best of both worlds – the long lifetime of phonons and the easy control/readout of solid-state qubits.

Acoustic transport of electrons (“phonon conveyor”)

An unconventional but noteworthy platform uses surface acoustic waves to literally carry flying electrons or excitons, effectively using acoustic waves to shuttle quantum particles. Early theoretical proposals (Cambridge, 2001) and experiments (McNeil et al., 2011) showed that a SAW in a piezoelectric semiconductor can pick up single electrons from a quantum dot and convey them along a channel, synchronizing their motion. This creates a moving “train” of single electrons that could serve as qubits or as a means to entangle distant static qubits by collision or interaction.

While this approach blurs the line between quantum acoustics and quantum electronics, it highlights the versatility of acoustic waves: they can act as a medium not just for phonons themselves as information carriers, but also for ferrying other quantum degrees of freedom (like electron charges or spins) between processor nodes. Such systems are still experimental and face challenges (loss and decoherence of the transported electron), but they broaden the scope of what “quantum acoustic” technologies might encompass in the future.

Regardless of platform, a common thread is that quantum acoustic devices require extreme isolation from environmental vibration and thermal noise. Experiments are conducted at millikelvin temperatures (dilution refrigerators) so that the thermal phonon occupancy $$n_{\text{th}} \approx 0$$ for GHz modes. (For example, a 5 GHz phonon has an energy $$\sim$$0.02 meV, which is comparable to a temperature of ~0.25 K; thus at 0.01 K, thermal excitations are essentially frozen out.) Devices are often nanofabricated on substrates like quartz, sapphire, or lithium niobate that have low acoustic loss. Even clamping losses (vibrations leaking into chip mounts) are addressed by phononic bandgap structures to confine vibrations.

In essence, a quantum acoustic processor looks like a chip with various acoustic circuits (resonators, waveguides, transducers) integrated alongside qubit circuits, all meticulously engineered to prevent unwanted sound leakage or absorption.

During operation, controlling a quantum acoustic system often means using electrical signals (microwave pulses) to manipulate the coupled qubits, which in turn create, absorb, or phase-shift phonons. For instance, to perform a single-phonon phase gate as in Qiao 2025, one would send a phonon wavepacket toward a qubit and simultaneously drive the qubit in a way that it imparts a controlled phase flip on the phonon’s quantum state.

Detection of phonons is typically done by quickly swapping the phonon back into a qubit excitation and measuring the qubit state (since directly measuring a single phonon in a resonator is hard without destroying it). Recent breakthroughs in number-resolving detection use the higher levels of a qubit (qutrit) as an effective “quantum microphone” that can tell 0, 1, or 2 phonons apart by absorbing them one by one. This is analogous to a photodetector that can count photons, but implemented in the acoustic domain.

Overall, the mechanics of quantum acoustic computing combine principles from multiple areas: quantum circuits (for qubit control), phonon physics (for acoustic mode engineering), and quantum optics (for interference and measurement techniques). The result is a flexible hybrid architecture. In a full quantum computer design, one might envision an array of superconducting qubits for fast operations, with phonon resonators serving as a long-lived quantum memory bank or as communication channels linking distant qubits on the chip. This synergy is a key theme in how quantum acoustics works in practice.

Comparison to Other Modalities

Quantum acoustic systems share some similarities with photonic quantum computing, as well as with solid-state qubit platforms, but also exhibit unique differences:

Versus Photonic (Optical) Systems

Both acoustic and optical modalities utilize bosonic carriers (phonons or photons) and can distribute entanglement between remote qubits.

However, a stark difference is in determinism and interaction strength. Photonic quantum computing often suffers from probabilistic operations – e.g. two photons do not naturally interact without special nonlinear processes, leading to schemes like KLM that are not deterministic. Phonons, by contrast, interact strongly with qubits and can be made to interact with each other mediated by qubits, enabling deterministic gates. The phase gate demonstrated with phonons has no exact analog in linear optics without adding nonlinearity.

Additionally, phonons in solids can have much longer coherence times than propagating photons in fiber or waveguides, since they don’t suffer absorption or radiation loss as readily (indeed, isolated acoustic modes can approach coherence times of seconds, whereas single photons typically propagate only milliseconds in fiber before loss).

On the other hand, photons travel at the speed of light and are easier to send long distances (meters to kilometers for networking). Phonons are effectively limited to on-chip or near-chip distances (a phonon would decay long before traveling macroscopic distances in material).

Thus, optical modalities excel in long-distance communication (quantum networks), while acoustic modalities are more naturally suited for on-chip interconnects and memories in a quantum processor.

Versus Superconducting Qubits

Superconducting qubit processors (the basis of many current quantum computers) typically use microwave photons confined in resonators or traveling in transmission lines to mediate coupling. Replacing or augmenting those photons with phonons can be seen as a variation on the circuit QED theme.

The advantage of phonons here is mainly their compactness and isolation. An acoustic resonator at 5 GHz can be microns in size, whereas a 5 GHz electromagnetic resonator on chip is centimeters long unless using high impedance techniques. This means phononic components could significantly reduce the footprint of quantum circuits and allow dense integration.

Also, as noted, acoustic modes don’t radiate away energy like microwave lines do – they can be more confined, potentially reducing cross-talk between components.

However, one disadvantage is that today’s superconducting qubits are designed to couple strongly to electromagnetic fields, not vibrations; introducing piezoelectric couplers can add loss or complexity to the qubit. Moreover, phonons being mechanical are susceptible to material defects and stress-induced frequency fluctuations (strain can shift the resonant frequency, akin to how dielectric noise affects microwave resonators).

In terms of maturity, superconducting qubits have multi-qubit gate schemes and algorithms demonstrated, whereas quantum acoustic operations have so far mostly been one- or two-qubit demonstrations serving as a hybrid extension to circuit QED.

Versus Trapped Ions or Neutral Atoms

Interestingly, trapped-ion quantum computers already use phonons – the collective vibration modes of ions – as a resource (the ions’ motional phonons mediate two-qubit gates).

However, in ion traps these phonons are internal to the ion crystal and not freely propagating in a solid. The “quantum acoustic modality” we discuss here instead uses engineered solid-state devices. Compared to ions/atoms, solid-state acoustic systems promise far greater scalability and integration (thousands of resonators could be lithographically fabricated on a chip, something not possible with ion traps or atom arrays at present).

They also can interface with superconducting circuits and other technologies directly. But ions/atoms still hold the lead in coherence – their phonon modes (in traps) can have coherence times of seconds, and the qubits (ion internal states) have extremely high fidelities. Solid-state phonons are catching up: as mentioned, certain acoustic modes have shown second-scale lifetimes, rivaling trapped-ion motional modes.

A key difference is tunability: Ion trap phonon modes are easily tuned by trap frequencies and are reconfigurable; solid acoustic resonators are fixed-frequency devices once fabricated (though one can have adjustable couplers or use multiple modes). Additionally, ion/atom platforms naturally produce identical qubits and interactions, whereas solid-state acoustic devices may suffer from fabrication disorder (frequency spread, defect-induced loss) that requires calibration or trimming.

Versus Other “Exotic” Modalities

Compared to emerging approaches like topological qubits or photonic continuous variables, quantum acoustic systems occupy a niche as a hybrid enhancer for existing qubit tech. They are not a completely standalone computing paradigm (one typically uses them in tandem with superconducting circuits or spins), so in that sense they are complementary rather than directly competing.

One could imagine, for example, a topological qubit (if realized) using an acoustic wave to communicate with another topological qubit – something photons could also do. Phonons might offer better on-chip integration in such scenarios.

Another interesting comparison is with quantum memory modalities: schemes like nuclear spins or trapped ions as memories could be rivaled by acoustic memories that store microwave quantum states. Already, researchers have coined the term “quantum acoustic memory” for devices that catch and release microwave photons as long-lived phonons. In summary, quantum acoustic systems often bridge modalities: they can connect superconducting (electrical) quantum systems with optical ones (via acousto-optic transducers ) or serve as a medium between different types of qubits.

This intermediary role distinguishes them from standalone modalities like pure photonics or pure spin qubits.

Current Development Status

As of 2025, the quantum acoustic modality is in the experimental stage, with rapid progress being made but still far from the scale of full universal quantum computers. Key achievements to date include: generation of single and multi-phonon quantum states; basic one- and two-qubit quantum logic operations using phonons (entangling qubits via phonons, single-phonon phase gates, etc.); and demonstrations of phonon-based quantum communication on-chip. These successes have mostly involved 2-3 qubit systems or single phonon modes serving as a memory or communication bus.

Some concrete indicators of the status:

Number of components

Experiments have involved at most a handful of qubits and acoustic resonators. For example, the 2025 phase gate experiment used two transmon qubits and one acoustic Mach-Zehnder interferometer channel. The 2019 entanglement experiment had two qubits and a single SAW link. There are no acoustic analogs yet of, say, a 50-qubit processor.

However, researchers have begun integrating multiple acoustic elements on one chip (e.g. two resonators entangled with two qubits, or a resonator network coupled to one qubit). The complexity is expected to grow as fabrication improves.

Coherence and fidelity

Phonon lifetimes in current devices range widely. SAW phonons in early devices had lifetimes of a few microseconds. Bulk acoustic modes have shown tens of microseconds up to a millisecond in special cases. The transmon qubits coupling to them usually have coherence times in the 10-50 microsecond range, which can be the limiting factor.

Gate fidelities involving phonons (like the phonon-phase gate) have not yet reached the ~$$>99%$$ level typical of the best superconducting qubit gates; they are more in the proof-of-concept stage (fidelities on the order of 90% or so, largely limited by decoherence during the phonon flight and interaction).

One bright point is that measurements of phonons (via qubits) can be quantum nondemolition in some schemes (counting phonons without destroying them), which is a desirable feature for quantum error correction in the future.

Integration with electronics

These experiments are done in dilution refrigerators with significant classical control hardware. The acoustic devices themselves are on-chip and often compatible with standard fabrication. For instance, thin-film lithium niobate on sapphire is a common platform, and integration with superconducting circuits lithographically is well established. Thus, in terms of manufacturability, quantum acoustic chips are not fundamentally more complex than superconducting qubit chips (just adding some extra patterning for the acoustic components).

A challenge though is design – simulation tools for large phononic circuits are still developing, as mechanical waves can be harder to model (they involve complex mode shapes, material anisotropies, etc.). Researchers are actively working on CAD tools for phononic quantum devices, and small foundry runs have produced test chips.

Notable projects and funding

The significance of quantum acoustics is increasingly recognized. For example, the U.S. Department of Defense’s Vannevar Bush Faculty Fellowship in 2024 was awarded to pursue phonon-based quantum computing research.

There are startups and academic collaborations focusing on quantum acoustic wave devices (like attempts to build quantum repeaters using mechanical modes, or hybrid quantum memory modules).

However, compared to modalities like superconducting qubits or ion traps, the community is smaller. Many quantum acoustics advances come from groups that also work in circuit QED or optomechanics rather than dedicated large companies (an exception being that big superconducting-qubit players like IBM/Google have internally explored using acoustic resonators for quantum memories).

In 2023-2025, we’ve seen an uptick in published results (Nature/Science papers each year) and a push toward scaling up: e.g. entangling two mechanical resonators on separate chips via phonons, or proposals to use phononic circuits for error-corrected memory.

Challenges remaining

Two big hurdles are loss and connectivity.

Acoustic loss comes from imperfect materials (two-level defects absorbing phonons, surface roughness scattering them, etc.), which currently limits lifetimes unless very carefully engineered (like the phononic crystal nanostructures for isolation).

Connectivity refers to wiring up many qubits with acoustic links: while it’s feasible to connect a pair of qubits with one acoustic resonator or waveguide, a large network would require switching or frequency multiplexing phonons to route quantum information among many nodes. Some theoretical work proposes using multiple acoustic modes (of different frequencies) as distinct channels, or dynamically tuning couplers to “connect” one qubit to different acoustic buses on demand. These ideas are in simulation/testing phase, not yet realized in hardware.

In summary, the current status of quantum acoustic computing is that of a promising auxiliary technology – it has achieved all the basic primitives (state transfer, storage, entanglement, gating) on a small scale, and now the task is to refine these operations to be high-fidelity and to scale the number of modes and qubits up.

Many in the field see near-term use cases in quantum memories or as quantum interconnects, which could be implemented sooner than a full-fledged “acoustic quantum computer.” The development trajectory is analogous to where superconducting qubits were perhaps in the mid-2000s: fundamental control was shown, and the decade that followed involved improving coherence and scaling from a handful of qubits to dozens – a path quantum acoustics is just beginning.

Advantages

Quantum acoustic modalities offer several compelling advantages that complement other quantum computing approaches:

Long Phonon Coherence Times

As discussed, phonons in isolated high-quality resonators can have extremely long lifetimes – potentially orders of magnitude longer than electromagnetic modes. Experiments have already shown mechanical $$T_2$$ times in the 1-100 ms range for carefully engineered devices, far beyond the coherence of a typical superconducting qubit (tens of µs) or even trapped-ion vibrational modes (which are limited by trap stability and other technical noise to maybe ms).

In principle, a phonon in a perfect crystal at low temperature has no fundamental loss mechanism except anharmonic decay, which can be minimized by design. This makes phonons ideal candidates for quantum memory – storing qubit states during quantum computations or communications until they are needed.

Strong, Deterministic Interactions

Unlike photons, which usually require mediators (nonlinear crystals, atoms, etc.) to interact, phonons in a solid naturally interact with qubits (via strain or piezoelectric coupling) with appreciable strength. This has two implications:

(1) One can achieve deterministic entangling operations between qubits and phonons, or between phonons themselves via qubit mediation, without relying on probabilistic protocols. The 2025 phase gate is a prime example, where a single phonon acquired a controlled phase shift every time it scattered off a qubit, not just occasionally.

(2) Phonon-mediated two-qubit gates (e.g. two distant qubits interacting through a common resonator mode) can be quite fast and high-fidelity because of the strong coupling – similar in spirit to ion-trap two-qubit gates that use shared motion. Essentially, the phonon can act as a “bus mode” connecting qubits, with coupling $g$ large enough to perform a gate within its coherence time.

On-Chip Integration and Miniaturization

Acoustic devices are compatible with standard microfabrication, meaning one can lithographically create arrays of resonators, waveguides, and transducers. Phononic circuits can be made very compact due to the short wavelength of sound at microwave frequencies.

For instance, a quarter-wavelength resonator at 5 GHz in a solid might be ~100 µm long (compare to ~1 cm for a 5 GHz microwave cavity on chip without special impedance engineering). This allows a dense integration of components for scaling up.

Moreover, integrating an acoustic layer with superconducting qubits or other electronics is feasible – some demonstrations use multi-layer processes (a piezoelectric layer for phonons on top of a silicon or sapphire substrate that hosts qubit circuits). The vision is a monolithic quantum chip where memory, communication, and computation elements are all co-located, and phonons play the role of wiring between them.

Relative Isolation (Low Crosstalk)

Phonons, being mechanical, do not directly couple to electromagnetic stray fields. This can reduce certain types of cross-talk. For example, two microwave qubits can interfere via microwave crosstalk if their lines are not perfectly isolated; by contrast, two qubits coupled via distinct acoustic resonators could be better isolated from each other’s influence, since vibrations remain localized if engineered properly (especially with phononic bandgap structures confining them).

Additionally, phonons aren’t prone to radiative loss into 3D space – they stay in the chip. This isolation also means less radiative leakage of quantum information; an excited phonon won’t emit out of the chip like a photon could from an open resonator.

Hybrid Connectivity

A big advantage of acoustic systems is they can interface disparate quantum objects. Since many solid-state qubits (superconducting qubits, spin qubits in diamond or silicon, quantum dots, etc.) reside in a solid matrix, phonons can couple to all of them through the crystal lattice.

For instance, a mechanical resonator can be coupled to a superconducting qubit and to an optical cavity (via optomechanics) and to a spin defect (via strain) – serving as a universal transducer of quantum information. Such hybrid couplings have been proposed and partially demonstrated (e.g. converting microwave qubit excitations to optical photons using an intermediate phonon mode ).

This versatility means quantum acoustic networks might connect nodes of different types – something purely photonic or purely electronic modalities can’t do as easily. In other words, phonons speak a “bilingual” language: they can talk to superconducting circuits in electric terms and to optical/atomic systems in mechanical terms, enabling hybrid quantum systems (like quantum repeaters or sensors that leverage multiple modalities).

Determinism in Linear Optics Analogs

As highlighted by the UChicago team, an acoustic platform can remove the reliance on probabilistic linear optical operations. Photonic one-way computing or linear optics quantum computing requires careful post-selection or large overhead to achieve gates, because beam splitters and detectors typically have success probabilities <1 for entangling operations. In an acoustic analog, one could incorporate superconducting qubits as inline elements that provide effective nonlinearities or conditioned operations on phonons, thereby creating a deterministic linear optical network using sound. This could significantly reduce resource overhead for approaches like boson sampling or cluster-state generation since one doesn’t have to repeat operations until success – the phonon interactions can be made to succeed essentially every time by design.

Potential for Error-Corrected Memory

Given their long lifetimes, phonon modes are being explored as quantum memory elements for error-correcting schemes. A recent concept is to store logical qubits in high-Q acoustic cavities that are coupled to qubits only when needed (to write or read the information). The long-lived phonon acts as a storage qubit that can sit idle with minimal noise. Some proposals even suggest encoding logical qubits in cat states or binomial states of a harmonic oscillator (a phonon mode) – an approach already pursued in microwave cavities – but using a phononic cavity instead, which might retain coherence longer than a microwave cavity of similar size.

The benefit is fewer quantum error correction cycles would be needed if the natural memory time is long. This is a speculative but exciting advantage: if realized, acoustic quantum memories could dramatically improve the scalability of quantum computers by offloading qubits from the main processor into storage without worrying they decohere quickly.

In short, quantum acoustic systems bring stability, strong coupling, and integrability to the table. They excel as a medium for quantum information that needs to be stored or shuttled around on a chip. As one article headline put it, “Tomorrow’s quantum computers could use sound, not light,” emphasizing that phonons’ lack of randomness in certain operations may give them an edge in building reliable quantum machines. Of course, these advantages must be weighed against challenges (below), but they form the rationale for the growing interest in quantum acoustics.

Disadvantages and Challenges

Despite the promise of quantum acoustic modalities, there are notable challenges and disadvantages that researchers are actively working to overcome:

Acoustic Loss and Decoherence

Phonons are subject to energy loss mechanisms in solid materials – mechanical dissipation from defects, interfaces, or thermoelastic effects. While photons can travel in superconducting circuits with extremely low loss (in 3D cavities or low-loss transmission lines), confining phonons often involves surfaces and interfaces that can sap energy. For example, a SAW propagating on a chip encounters surface roughness and any surface adsorbates, leading to scattering and absorption.

Even in bulk resonators, two-level system (TLS) defects in the crystal or amorphous interfaces can absorb phonons (much like they cause dielectric loss for qubits). Achieving the ultra-long lifetimes requires exceptional material purity and isolating the resonator from supports (hanging resonators or phononic crystal isolation). This is technologically challenging. Today’s phonon Q’s, while high, are still typically below their theoretical limits due to such imperfections.

Additionally, dephasing can occur if the phonon frequency fluctuates (e.g. from strain or temperature drifts in the substrate). Maintaining phase stability of a mechanical mode over long times is non-trivial – it requires environmental control akin to shielding qubits from magnetic noise, here one must shield from vibration and temperature fluctuations.

Coupling to Qubits Induces Loss

An ironic but important point is that the moment you couple a “perfect” phonon resonator to a qubit for control, you often introduce loss. The press release of the 2025 work notes: “The reason the [phonon] lifespan is so short is because the phonons are coupled to a qubit… like grabbing a ringing bell to muffle it.”. The qubit’s dissipation (and any loss in the coupling circuitry) provides a channel for the phonon to decay.

In essence, making phonon operations deterministic (strong coupling) can inversely shorten coherence by “opening” the system to the qubit’s environment. Decoupling preserves phonon coherence but then you can’t use it. This trade-off means there’s an optimal coupling regime – strong enough for operations, weak enough to not kill the phonon too fast. Improving qubit coherence and using tunable couplers (so that the phonon is only strongly coupled during gate operations, and otherwise stored in isolation) are active areas of work.

Scaling and Routing

In an optical quantum computer, beams of light can cross paths (with some engineering) or be dynamically routed using beam splitters and switches, and many modes can coexist with different frequencies or polarizations. In acoustic systems, the concept of a “wire” is more literal – a phonon waveguide on a chip can carry phonons, but crossing two acoustic waveguides is difficult without crosstalk (vibrations would likely couple).

There are no straightforward acoustic analogs of optical fiber networks; any interconnect on chip must be carefully designed to prevent unwanted coupling. As a result, creating a large network of phonon interconnects is challenging – it might resemble a maze of coupled resonators or require time-multiplexing signals. Fanout is also an issue: splitting one phonon into many paths will divide its quantum (one cannot clone a quantum state, so distributing quantum info acoustically means either splitting an amplitude or using multiple sequential emissions).

Thus, the architecture of an acoustic quantum processor may need to be somewhat serial or limited in connectivity, compared to superconducting qubit chips that have many microwave lines and can route signals relatively freely. Some proposals for multi-phonon routing involve using different frequencies (each resonator or channel operating at a distinct GHz frequency so they don’t interfere), but frequency crowding could become an issue beyond a dozen or so modes.

Speed (Slow Phonons)

The low speed of sound, while advantageous for compactness, can be a disadvantage for speed. A phonon taking, say, 1 µs to travel between qubits is 10,000 times slower than a photon taking ~100 ps for the same distance. This means communication latency on chip is higher with phonons. If one envisions a large acoustic network, the delay could bottleneck the clock speed of a quantum processor (1 µs is huge compared to typical two-qubit gate times of 20-50 ns in superconducting systems).

Moreover, gating operations that involve shuttling phonons around or waiting for them to traverse interferometers will inherently be slower than electrical signal-based gates. This doesn’t mean phonon-based quantum computers would be 10,000× slower overall – many operations can still be local – but it does imply that using phonons for everything (especially long-distance communication on the chip) could limit throughput.

In practice, a hybrid design might reserve phonons for what they are best at (memory, occasionally moving data) and use fast electrical gates for local operations.

Limited Distance and Range

While photons can travel kilometers in fiber (with some loss), phonons attenuate within centimeters or less in solid media (even the best chips will have propagation loss or eventually the modes will radiate into supports).

Quantum acoustic systems are therefore confined to local or intermediate-range connections – essentially within a single cryostat or chip. They are not suitable for long-haul quantum communication by themselves (though one can convert phonons to photons via transducers as mentioned). For distributed computing between cryogenic nodes, one would still likely convert to optical.

Thus, the role of phonons is envisioned more for intra-device links or perhaps linking modules in a multichip package at best, not for connecting quantum computers across distances – a realm where optics remains king.

Fabrication Uniformity and Tuning

Solid-state devices suffer from manufacturing imperfections. Two nominally identical acoustic resonators might have slightly different frequencies due to tiny variations in dimensions or film stress. Unlike qubits (whose frequencies can often be tuned in situ by flux or voltage), many mechanical resonators are not in situ tunable (some are developing tunable mechanical resonators using electrostatic or nonlinear effects, but it’s not as straightforward as a transmon’s flux tuning). This means building a large array of phonon devices might require post-fabrication tuning (e.g. laser trimming or applying strain) to get them on frequency. Without tuning, cross-talk and frequency collisions could occur in a multi-mode system.

This challenge is similar to that faced in photonic integrated circuits (where resonances have to be tuned with heaters, etc.), but doing so at millikelvin is harder (heaters introduce heat; one could use mechanical strain or electric fields to fine-tune acoustic cavities, which is being researched).

Overall, managing a complex acoustic circuit will require new solutions for calibration and dynamic control of mechanical resonance frequencies.

Measurement Backaction and Efficiency

Reading out phonon states usually involves a qubit, as mentioned. This extra step can be a bottleneck – the readout fidelity is limited by qubit readout fidelity, and there’s added backaction: measuring the qubit typically collapses the phonon state as well (unless doing a QND measurement scheme).

The detection efficiency of single phonons is effectively the efficiency of the qubit state detection, which might be 95-99% in a good setup. In contrast, single-photon detectors in optics can have >99% efficiency these days, and ion trap fluorescence detection can be >99.9%.

Thus, acoustic systems currently rely on intermediary detectors that may not be as efficient or could collapse the state too strongly. Advances in QND phonon detection (e.g. using ancilla qubits or repeated interactions to gently measure phonon number ) are needed to make error-corrected operations feasible without destroying the state being stored.

In summary, while quantum phononics holds great potential, it is not a plug-and-play replacement for photons or traditional qubits; rather, it introduces its own engineering hurdles. The field is actively addressing these by improving materials (e.g. high-purity acoustic cavities, phononic bandgap shields), developing tunable and modular structures, and integrating error mitigation techniques. It’s worth noting that many challenges are of an engineering nature, not fundamental limits – for instance, slow phonon speed is just a fact to design around, not a fatal flaw. And some disadvantages like short range are acceptable if the use case is on-chip only. The coming years will show whether solutions like phononic integrated circuits with low-loss materials and clever coupling designs can mitigate most of these issues, enabling the advantages to shine through.

Impact on Cybersecurity

From a cybersecurity perspective, the quantum acoustic modality does not introduce fundamentally new threats compared to other quantum computing approaches – rather, it fits into the broader quantum computing timeline that concerns cryptographers. However, there are a few points to consider:

Timeline to Breaking Encryption

Quantum acoustic processors are still in early development, which means they are not near achieving the scale needed to threaten RSA or other cryptographic primitives.

The most advanced quantum computers threatening encryption today (circa 2025) are based on superconducting qubits or ion traps with tens or hundreds of qubits. Quantum acoustic systems, by contrast, are at the stage of demonstrating a few-qubit operations.

So in the near term, this modality does not accelerate the arrival of quantum decryption capabilities. If anything, it might extend the timeline by providing another path to scaling (as a supportive technology for superconducting qubits), but we are still talking about years of development before quantum acoustic hybrid systems produce large, stable qubit counts. For now, cybersecurity professionals are primarily watching other modalities for quantum advantage milestones.

Synergistic Threat

In the longer term, if phonon-based memories or interconnects significantly aid the construction of a scalable quantum computer (for instance, allowing superconducting platforms to double or triple their effective qubit count by using phonon memory modules), then one could argue this modality indirectly contributes to the threat to classical cryptography.

It’s part of the ecosystem of technologies that could make a million-qubit machine possible (which is what’s needed for breaking RSA-2048 via Shor’s algorithm with error correction). So while a “phonon quantum computer” alone isn’t racing to break encryption, its integration into hybrid designs could speed up progress toward that goal.

It’s a piece of the puzzle in quantum scalability, and security analysts should be aware of advances in all modalities, including acoustic, when estimating the quantum threat timeline.

Side-Channel Considerations

Classical cybersecurity has taught us that sound can be a side-channel (e.g., acoustic emanations from keyboards or CPUs can leak information). In quantum computing, one ironically tries to isolate from sound (vibrations) to preserve coherence. Quantum acoustic systems confine their phonons, but one might wonder: could there be acoustic side-channel risks? If an adversary could generate external vibrations at specific frequencies, could they disturb or even read out the state of an acoustic quantum memory?

Directly reading out seems highly improbable (you’d need to interfere at the quantum level, which essentially means spoiling the coherence). However, deliberate acoustic interference could serve as a denial-of-service: injecting vibration noise to decohere the phonon modes. This is akin to shining a bright light into an optical quantum computer to noise it out.

So, if quantum acoustic devices were ever used in a secure multi-tenant quantum cloud, one would need to ensure strong vibration isolation so that one user’s activity (or a malicious actor) cannot mechanically disturb another’s quantum acoustic memory. In essence, vibrational noise becomes a new factor in quantum security – something already well-known in quantum lab engineering but now with potential cybersecurity implications if attackers try to exploit it.

Post-Quantum Cryptography (PQC) Implications

The rise of any quantum computing modality underscores the need for transitioning to PQC. Quantum acoustic computing doesn’t break new cryptographic algorithms that other quantum computers wouldn’t; it would run the same algorithms (Shor, Grover, etc.) if large enough. Thus, its impact is to reinforce the message: assume that within a couple of decades (if not sooner) we will have quantum computers (maybe hybrid including acoustic) that threaten current encryption. As such, adopting PQC (quantum-resistant algorithms) remains crucial. In fact, the interdisciplinary nature of quantum acoustic research – bridging mechanical engineering and quantum info – highlights how broad the quantum R&D base is, meaning surprise breakthroughs could come from unexpected angles (perhaps a novel phononic processor design leaps ahead). This breadth of effort is why conservative planning assumes a quantum-capable adversary sooner rather than later.

Use in Cryptographic Devices: On the flip side, quantum acoustic devices might find uses in securing communication. For instance, a long-lived phonon memory could be part of a quantum repeater for quantum key distribution (QKD) , or acoustic sensors might help detect side-channel attacks (e.g., listening to a device’s vibrations). These are speculative, but as quantum sensing and computing converge, one can imagine mechanical resonators being used in security devices (like a phononic quantum random number generator or a tamper sensor that detects intrusion by changes in vibrational modes).

In conclusion, cybersecurity professionals should view quantum acoustic computing as an integral part of the quantum computing landscape – not a radical new threat on its own, but as a contributor to eventual quantum capabilities. The modality reinforces the urgency of migrating to PQC in a timely fashion.

Additionally, as quantum hardware diversifies, security experts must consider all the ways quantum operations could be disrupted or leaked – including through acoustic means. Just as classical security had to account for electromagnetic emissions, future quantum security might need to account for literal “sound” at the quantum scale. For now, the main takeaway is that the quantum acoustic modality is another sign that progress toward powerful quantum computers is multifaceted and ongoing, underscoring that the quantum threat to encryption is a matter of “when, not if,” even if this particular approach is still in an early phase.

Future Outlook

The future of quantum acoustic computing looks promising as both a standalone research direction and a enabling technology for hybrid quantum systems. Here are some expectations and developments on the horizon:

Scaling Up and Modular Quantum Architectures

In the coming years, we can expect experiments that go from the current 2-3 qubit demos to systems with perhaps 5-10 qubits and multiple resonators.

One potential architecture is a modular quantum computer where each module (say 4-5 superconducting qubits) is connected to other modules via phonon waveguides or resonators, forming a larger composite processor. Phonons could carry entanglement between modules on a chip or even between chips within the same cryostat. This modular approach, enabled by acoustic links, can circumvent some wiring limitations of trying to fully connect, say, 100 qubits all with microwave lines (which would be very crowded). Instead, acoustic buses can act as “quantum backplanes” linking clusters of qubits. Early versions of this are being attempted (for example, entangling qubits on separate chips through a shared mechanical resonator has been demonstrated in 2025 ).

Over the next 5-10 years, scaling to tens of modules connected by phonons might be achievable, which would validate phononics as a pathway to scale beyond what monolithic superconducting chips can do.

Improved Materials and Lifetimes

We will likely see quantum acoustic cavities with Q-factors in the $$10^8$$-$$10^9$$ range become standard in labs. New materials like high-purity crystalline films (e.g. epitaxial AlN or GaN on diamond, or single-crystal quartz devices) and better nanofabrication (etching techniques that minimize surface damage) are actively being pursued. Achieving resonator coherence times in the 0.1-1 second range at GHz frequencies would be a game changer, as it would surpass even some of the best electromagnetic cavity memories. One particular avenue is the use of phononic bandgap shields to eliminate radiation loss: essentially building acoustic “mirror chambers” around a resonator so that no vibrational energy can leak out into the substrate.

These techniques could make phonon modes incredibly stable. As noted by Prof. Cleland, the next hurdle is extending phonon lifetimes 100× from microseconds to milliseconds , and theoretically this is within reach by reducing coupling and loss. Such improvements will come hand-in-hand with better coupling strategies that can be turned on/off to preserve isolation when needed.

Error Correction and Phonon-Based Qubits

Today, phonons are mostly used as bus modes or memories for superconducting qubits. In the future, one could imagine encoding quantum information directly in phononic modes as logical qubits. For instance, a single phonon mode can host a bosonic logical qubit (using cat codes or binomial codes). Researchers have already done this with microwave photon modes; doing it with a long-lived phonon mode is a logical next step. If a single phononic mode can be error-corrected (by coupling to a qubit ancilla that corrects its state every so often), it could serve as a fully quantum memory.

There is also the intriguing idea of phononic cluster states – entangling many phonon modes into a large cluster that could be used for one-way quantum computing (analogous to photonic cluster states). Some theoretical proposals (including Qiao 2023’s notion of “linear mechanical quantum computing”) hint at using phonon interferometry for measurement-based quantum computing. This would require generating many entangled phonon modes, perhaps via a network of beam splitters and squeezers (drawing from optomechanics to produce squeezed phonon states, etc.). While far off, it suggests a future where phonons aren’t just auxiliaries to qubits but are themselves the core qubit array.

Integration with Quantum Networking

Phonons will likely play a role in quantum repeaters and transducers. A phonon can couple to both microwave and optical domains, so it can be used to transfer quantum states between a microwave-based quantum computer (e.g. a superconducting qubit processor) and optical fiber for long-distance communication. Already, experiments have shown microwave-to-optical conversion using mechanical systems as intermediaries. As this technology matures, one could see phononic chips sitting at the edge of dilution refrigerators converting qubit states to photons for secure communication (QKD or connecting quantum computers into clusters).

The quantum internet of the future might use phonon-based devices as the “phone line” between superconducting quantum processors and telecom photons.

Commercial and Practical Outlook

In terms of commercialization, quantum acoustic tech might first appear not as a full computer but as specific components: for example, a quantum acoustic memory module that can be added to a superconducting quantum computer to enhance its capabilities. If a company can build a phonon memory that stores qubits for, say, 1 ms with high fidelity and retrieves them on demand, that could be a valuable product to extend algorithm runtimes or implement complex protocols (like swap networks or parallel computation) on existing quantum processors.

We might also see quantum sensors improved by acoustic modes – e.g. using entangled phonons to measure forces or accelerations at quantum-limited precision (since mechanical systems are natural sensors). These would be spin-offs of the main effort but could find niche applications (much like how some quantum computing tech led to improved clocks or MRI sensors along the way).

As quantum acoustic researchers push the boundaries, their innovations in materials, control electronics, and system integration will likely benefit other modalities. For instance, techniques for dealing with two-level system defects in mechanical resonators could also improve superconducting qubits (which suffer from TLS in dielectrics). Or methods to isolate acoustic modes could inspire better isolation of electromagnetic modes.

In this sense, the modality’s development contributes to the overall quantum engineering knowledge base. We can expect more convergence of ideas – for example, using error-correcting codes initially designed for photonic qubits now being adapted to phononic qubits, or vice versa.

Broader Impacts

If phonon-based quantum tech becomes mainstream, it could also influence how we think of information processing in classical terms. For example, one could envision classical acoustic signal processors at low temperatures that preprocess microwave signals in a quantum computer (there’s already work on using acoustic waves for filtering and frequency conversion in classical RF electronics). On the quantum algorithm side, having a mix of qubits and resonator modes might enable new algorithms that leverage a kind of quantum RAM (random access memory) – indeed the same UChicago group proposed a QRAM using phonons. This could make certain quantum algorithms (those requiring large data access) more feasible.

So the future might see quantum computers where qubits do the logic and phonons serve as the memory bank that feeds data into computations on the fly.

In conclusion, the quantum acoustic modality is evolving from a novel experiment into a practical toolkit for quantum technology. As my broader taxonomy hints, it’s one of the “exotic and emerging approaches,” but one that is quickly maturing.

The optimistic view, echoed by experts like Cleland and Jiang, is that phonons might even rival photons for building tomorrow’s quantum computers due to their deterministic behavior and integrability. Over the next decade, we’ll see whether quantum acoustic systems can overcome their challenges and indeed deliver on that promise. If they do, the result could be quantum processors that are as fast and powerful as the best current designs, but with added robustness and scalability – perhaps fulfilling the vision of a solid-state, sound-based quantum computer that runs complex algorithms with ease.