Quantum Computing
PostQuantum.com – Industry news and blog on Quantum Computing, Quantum Security, PQC, Post-Quantum, Quantum Tech
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Quantum Fourier Transform (QFT)
Quantum Fourier Transform (QFT), like a physical Fourier transform, takes a time-domain wave and represents it in the frequency domain. In the quantum case, the “time-domain” is the computational basis amplitude distribution, and the “frequency-domain” is another basis where the basis states correspond to different phase gradients across the original…
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Hadamard Gate: The Gateway to Superposition
The Hadamard gate takes a qubit and puts it into an equal superposition of “0” and “1” (with a relative phase of + or -). It has a simple matrix but a profound impact: it enables parallelism and interference in quantum algorithms. Historically rooted in Hadamard matrices from mathematics, it…
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Quantum Superposition: How Qubits Live in Many States at Once
Quantum computing promises to solve problems that stump even the fastest classical supercomputers. At the heart of this promise is a mind-bending phenomenon: quantum superposition. In simple terms, superposition allows quantum bits—or qubits—to occupy multiple states at the same time, unlike ordinary bits which are firmly either 0 or 1.…
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Colliding Waves: How Quantum Interference Powers Quantum Computing
Quantum interference remains the cornerstone of quantum computing’s promise. It’s the feature that distinguishes quantum computation from just a random quantum jumble. A quantum computer is not powerful simply because it can have many states at once – if that were all, measuring would give a random one and it…
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Understanding “Polynomial Time” – Why Faster Algorithms Matter
Quantum computing has emerged as a new frontier of great-power competition in the 21st century. Nations around the world view advanced quantum technologies as strategic assets—keys to future economic prowess, military strength, and technological sovereignty. Governments have already poured over $40 billion into quantum research and development globally, launching national…
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Key Principles and Theorems in Quantum Computing and Networks
The landscape of quantum computing and quantum networks is an exciting frontier where physics and cybersecurity intersect. We’re witnessing the early days of this quantum revolution. As quantum hardware scales and quantum protocols move from labs to real-world deployment, security experts will need to collaborate with physicists like never before.…
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Qubits: A Brief Introduction for Cybersecurity Professionals
A qubit is the quantum analog of a classical bit – it’s the basic unit of quantum information. However, unlike a classical bit that can only be 0 or 1 at any given time, a qubit can exist in a combination of both 0 and 1 states simultaneously. This property…
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Bell States: An Introduction for Cybersecurity Professionals
Bell states are a set of four specific quantum states of two qubits (quantum bits) that are entangled. In simple terms, an entangled pair of qubits behaves as one system, no matter how far apart they are. Bell states are the simplest and most extreme examples of this phenomenon. They…
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Kuperberg’s Algorithm and its Impact on Post-Quantum Cryptography (PQC)
Kuperberg’s algorithm is an impressive quantum algorithmic achievement that expands the boundary of what quantum computers might do beyond the original realm of Shor’s algorithm. It demonstrates that even some non-trivial group problems (like the dihedral hidden subgroup problem) are easier for quantum computers than for classical ones, albeit not…
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Balancing Quantum Computing Hype and Hope
Quantum computing stands at the intersection of immense promise and intense hype. As someone who had led cybersecurity teams (including serving as an interim CISO for Fortune 500 companies) and was now investing in a quantum computing startup, I found myself navigating two contrasting narratives. On one hand, I am…
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Why I Chose Photonic Quantum Computing
Choosing photonic quantum computing for my startup is equal parts ambition and pragmatism. The ambition is that photons, with their long coherence and networking talent, could unlock scalable quantum computers without the cryogenic baggage of other approaches. The pragmatism was that by immersing myself in this cutting-edge field, I could…
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Quantum Computing Hype and Fear: Same Song, New Verse
Another year, another wave of "quantum computers are about to crack all our encryption" fear-mongering. It’s 2012, and I’m getting déjà vu reading headlines proclaiming the imminent doom of RSA and other cryptography. I've been writing about this for at least 10 years. Ever since Peter Shor unveiled an algorithm…
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Quantum Computers Intro
I remember the first time I heard the phrase “quantum computer” about a ten years ago. I pictured something out of a sci-fi movie - maybe a glowing box humming with mystical power. As a techie who spends a lot of time worrying about encryption and security, my skeptical eyebrow…
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Quantum Computing Hardware Update
In summary, as 2006 ends I remain confident yet realistic. We’ve seen genuine, hard-won progress in quantum hardware: superconducting circuits entangling, ions scaling up with superb control, photons performing logic, and even completely different technologies proving their quantum chops. We’ve also seen that each platform has serious challenges to overcome…
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Are Quantum Computers a Real Threat?
Our conclusion is that quantum computers are not an imminent threat to cybersecurity. They are a fascinating technology and potential threat in the long term, but certainly not something that keeps me awake at night today. For our clients such as governments and critical infrastructure operators, the prudent advice is…
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