Q-Day
PostQuantum.com – Industry news and blog on Quantum Computing, Quantum Security, PQC, Post-Quantum, Q-Day, Y2Q
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Capability B.4: Qubit Connectivity & Routing Efficiency
Qubit connectivity refers to which qubits can interact directly (perform two-qubit gates) with each other. This is often visualized as a connectivity graph: each node is a qubit, and an edge between two nodes means those qubits can be coupled for a two-qubit gate. Some hardware has a dense graph…
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4,099 Qubits: The Myth and Reality of Breaking RSA-2048 with Quantum Computers
4,099 is the widely cited number of quantum bits one would need to factor a 2048-bit RSA key using Shor’s algorithm – in other words, the notional threshold at which a quantum computer could crack one of today’s most common encryption standards. The claim has an alluring simplicity: if we…
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What Will Really Happen Once Q-Day Arrives – When Our Current Cryptography Is Broken?
As the world edges closer to the era of powerful quantum computers, experts warn of an approaching “Q-Day” (sometimes called Y2Q or the Quantum Apocalypse): the day a cryptographically relevant quantum computer can break our current encryption. Unlike the Y2K bug—which had a fixed deadline and was mostly defused before…
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Q-Day Predictions: Anticipating the Arrival of CRQC
While CRQCs capable of breaking current public key encryption algorithms have not yet materialized, technological advancements are pushing us towards what is ominously dubbed 'Q-Day'—the day a CRQC becomes operational. Many experts believe that Q-Day, or Y2Q as it's sometimes called, is just around the corner, suggesting it could occur…
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Harvest Now, Decrypt Later (HNDL) Risk
"Harvest Now, Decrypt Later" (HNDL), also known as "Store Now, Decrypt Later" (SNDL), is a concerning risk where adversaries collect encrypted data with the intent to decrypt it once quantum computing becomes capable of breaking current encryption methods. This is the quantum computing's ticking time bomb, with potential implications for…
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Cryptographically Relevant Quantum Computers (CRQCs)
Cryptographically Relevant Quantum Computers (CRQCs) represent a seismic shift on the horizon of cybersecurity. In this article, we’ve seen that CRQCs are defined by their ability to execute quantum algorithms (like Shor’s and Grover’s) at a scale that breaks the cryptographic primitives we rely on daily. While still likely years…
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Neven’s Law: The Doubly Exponential Surge of Quantum Computing
In 2019, Google’s Quantum AI director Hartmut Neven noticed something remarkable: within a matter of months, the computing muscle of Google’s best quantum processors leapt so quickly that classical machines struggled to keep up. This observation gave birth to “Neven’s Law,” a proposed rule of thumb that quantum computing power…
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CRQC Readiness Index Proposal
This proposal outlines a composite, vendor‑neutral “CRQC Readiness” indicator. It intentionally avoids one‑number vanity metrics (like only counting qubits) and instead triangulates from three ingredients that actually matter for breaking today’s crypto: usable (logical) qubits, error‑tolerant algorithm depth, and sustained error‑corrected operations per second.
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Understanding FIPS 140: A Cornerstone of Cryptographic Security
FIPS 140 (Federal Information Processing Standard 140) is a U.S. government computer security standard that specifies security requirements for cryptographic modules - the hardware or software components that perform encryption and other cryptographic functions. In simpler terms, FIPS 140 sets the ground rules for how encryption engines (in everything from…
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Q-Day (Y2Q) vs. Y2K
In the late 1990s, organizations worldwide poured time and money into exorcising the “millennium bug.” Y2K remediation was a global scramble. That massive effort succeeded: when January 1, 2000 hit, planes didn’t fall from the sky and power grids stayed lit. Ever since, Y2K has been held up as both…
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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…
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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…
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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…
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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…
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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…
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