All Q-Day, Y2Q Posts
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Quantum Computing
What’s the Deal with Quantum Computing: Simple Introduction
Quantum computing holds the potential to revolutionize fields where classical computers struggle, particularly in areas involving complex quantum systems, large-scale optimization, and cryptography. The power of quantum computing lies in its ability to leverage the principles of quantum mechanics—superposition and entanglement—to perform certain types of calculations much more efficiently than classical computers.
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Post-Quantum, PQC, Quantum Security
The CRQC Quantum Capability Framework
This guide is a detailed, end‑to‑end map for understanding what it will actually take to reach a cryptographically relevant quantum computer (CRQC), i.e. break RSA-2048 - not just headline qubit counts. A CRQC must meet two conditions: the algorithmic requirements of the target attack and the hardware capabilities needed to execute it fault-tolerantly. The CRQC Quantum Capability Framework organizes these hardware capabilities into nine interdependent…
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Post-Quantum, PQC, Quantum Security
Brassard–Høyer–Tapp (BHT) Quantum Collision Algorithm and Post-Quantum Security
The Brassard–Høyer–Tapp (BHT) algorithm is a quantum algorithm discovered in 1997 that finds collisions in hash functions faster than classical methods. In cryptography, a collision means finding two different inputs that produce the same hash output, undermining the hash’s collision resistance. The BHT algorithm theoretically reduces the time complexity of finding collisions from the classical birthday-paradox bound of about O(2n/2) (for an n-bit hash) down…
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Post-Quantum, PQC, Quantum Security
Capability D.3: Continuous Operation (Long-Duration Stability)
One of the most critical requirements for a cryptographically relevant quantum computer (CRQC) is continuous operation - the ability to run a complex quantum algorithm non-stop for an extended period (on the order of days) without losing quantum coherence or needing a reset. In practical terms, the entire quantum computing stack - qubits, control electronics, error-correction processes, cooling systems - must sustain stable performance for…
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Post-Quantum, PQC, Quantum Security
Capability D.1: Full Fault-Tolerant Algorithm Integration
Imagine a quantum computer that can execute an entire algorithm start-to-finish with errors actively corrected throughout. Full fault-tolerant algorithm integration is exactly that: the orchestration of all components - stable logical qubits, high-fidelity gates, error-correction cycles, ancilla factories, measurements, and real-time feedback - to run a useful quantum algorithm reliably from beginning to end. This capability is essentially the “system integration” of quantum computing, bringing…
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Post-Quantum, PQC, Quantum Security
Capability D.2: Decoder Performance (Real‑Time Error Correction Processing)
In a fault-tolerant quantum computer, qubits are continuously monitored via stabilizer measurements (producing “syndrome” bits) to detect errors. The decoder is a classical algorithm (running on specialized hardware) that takes this rapid stream of syndrome data and figures out which qubits have experienced errors, so that corrections can be applied immediately. Achieving real-time decoding at scale is enormously challenging: a CRQC may need to handle…
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Post-Quantum, PQC, Quantum Security
Capability C.2: Magic State Production & Injection (Non-Clifford Gates)
Magic states are an essential “extra ingredient” for universal quantum computing, often metaphorically likened to a magic catalyst enabling otherwise impossible operations. Quantum algorithms require not only robust qubits and error correction, but also a way to perform non-Clifford gates - operations outside the easy Clifford group. These non-Clifford gates (like the T gate or controlled-controlled-Z) are the key to achieving universal quantum computation, yet…
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Post-Quantum, PQC, Quantum Security
Capability C.1: High-Fidelity Logical Clifford Gates
Cryptographically Relevant Quantum Computers (CRQCs) will rely on a suite of core capabilities - and high-fidelity logical Clifford gates are among the most essential. This capability refers to performing the fundamental set of quantum logic operations (the Clifford gates: Pauli X, Y, Z flips; the Hadamard (H); the phase gate (S); and the controlled-NOT (CNOT), among others) on logical qubits with speed and reliability. In…
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