Quantum Computing Research

This page is my personal scrapbook of interesting links, sessions and more around Quantum Computing. After being asked me to share a list, I decided to create a public page. Don’t critique the layout, one day I will get around to correctly attributing and notating content.
Schrodinger Telling Cat to stop Miaowing

NIST & NSA focus on Post-Quantum cryptography rather than QKD or QCrypt

Post-Quantum Cryptography: Digital Signature Schemes – Call for Proposals due June 1, 2023 NSA current opinion is … “NSA views quantum-resistant (or post-quantum) cryptography as a more cost effective and easily maintained solution than quantum key distribution.”

(This is a good ‘level set’ article) Quantum circuits still can’t outperform classical ones when simulating [larger] molecules

Simulations Using a Quantum Computer Show the Technology’s Current Limits It sounds bad when they say “… the team could only obtain meaningful results for a very small 6-atom chunk of the crystal lattice; if they increased the size to just 10 atoms, the noise overwhelmed the output.” BUT, remember the article also says “Compared to our expectations in 2005, [these results] are absolutely amazing, but they also show how much work is still ahead of us.”

Error correction has been reliable in digital computing for decades. How will we get there for Quantum Computing.

How Quantum Computers Will Correct Their Errors Here’s the key quotes … “The result shows that a fault-tolerant quantum computer is possible” while bearing in mind that “… the advantage granted by error correction won’t be seen until quantum computers have reached about 100 logical qubits. Such a machine would require about 1,300 physical qubits.”

U.S. National Security Agency (NSA) Releases FAQ Document Discouraging the Use of QKD

National Security Agency – Frequently Asked Questions – Quantum Computing and Post-Quantum Cryptography Here’s the key quote …
“NSA does not consider QKD a practical security solution for protecting national security information.”

Found a source for Quantum news.

Just subscribe to the daily newsletter at Inside Quantum Technology Newsletter. You will have to provide a name and an email address, and in return you will receive a daily summary on quantum news.

D-Wave uses quantum annealing to demonstrate a quantum computational advantage could be achieved over classical means.

A quantum computer just solved a decades-old problem three million times faster than a classical computer
The real significance of the experiment rather lies in the proof that a computational advantage can already be achieved using existing quantum methods to solve a valuable materials science problem.

Artificial Intelligence Solves Schrödinger’s Equation

Artificial Intelligence Solves Schrödinger’s Equation
This is about quantum chemistry rather than quantum computing, but still interesting. “The electronic Schrödinger equation can only be solved analytically for the hydrogen atom, and the numerically exact full configuration-interaction method is exponentially expensive in the number of electrons. Quantum Monte Carlo methods are a possible way out: they scale well for large molecules, they can be parallelized and their accuracy has, as yet, been only limited by the flexibility of the wavefunction ansatz used. Here we propose PauliNet, a deep-learning wavefunction ansatz that achieves nearly exact solutions of the electronic Schrödinger equation for molecules with up to 30 electrons. PauliNet has a multireference Hartree–Fock solution built in as a baseline, incorporates the physics of valid wavefunctions and is trained using variational quantum Monte Carlo. ”

China Stakes Its Claim to Quantum Advantage

China & Quantum Advantage – 200 seconds vs 2.5 billion years – If you ask the right question
Jiuzhang is a photonic quantum computer. Google claimed advantage already on their Sycamore device based on superconducting materials. [See stories and reactions below.] “One difference between Jiuzhang and Google’s Sycamore is that the photonic prototype is not easily reprogrammable to run different calculations. Its settings were effectively hard coded into its optical circuits.” Jiuzhang took 200 seconds to provide an answer, they claim the world’s fastest supercomputer would spend 2.5 billion years to carry out the same calculations.
Sooooo, they configured the computer especially to run this specific test. Impressive, but not flexible.

China is shooting for quantum advantage

China is shooting for quantum advantage
In the race to demonstrate “quantum advantage”, which basically just means showing that you can do something faster with a quantum computer than we can do with any existing classical computer, it is important to note that this does not have to be useful data. We’re not talking about a useful machine or a scalable machine or a universal machine. Consider the analogy of the Wright brothers’ first airplane, which gave a proof of principle. The Chinese test is an answer to the skeptics, who said that you would never get any speedup with a quantum computer.
Tell Schrodinger I Survived Photo of Cat

Another step towards quantum internet

Teleportation Systems Toward a Quantum Internet
” … we achieve conditional quantum teleportation of time-bin qubits … We measure teleportation fidelities of ≥ 90% … we teleport qubits over 22 km of single-mode fiber while transmitting qubits over an additional 22 km of fiber. Our systems, which are compatible with emerging solid-state quantum devices, provide a realistic foundation for a high-fidelity quantum Internet with practical devices.”

Quantum networking creeps slowly forward.

Researchers entangle quantum memory at facilities over 50km apart
” … That’s a big step up from the previous record of 1.4km. … For a 50km-long fiber path, this led to some rather low efficiencies, on the order of 10-4. Which means the time to achieve entanglement went up—in this case to over half a second. And that’s a problem, because the typical lifetime of a qubit stored in this memory is 70 microseconds, much shorter than the entanglement process. So the approach definitely falls into the “not quite ready for production” category.”

Inside the high-stakes race to make quantum computers work

Inside the high-stakes race to make quantum computers work
Quantum computers could help explain some of the most fundamental mysteries in the universe and upend everything from finance to encryption – if only someone could get them to work.

Cartoon of Schrodinger getting arrested, and saying you cannot arrest me as i am in a superposition of innocent and guilty guilty AND innocent

Quantum computers are so different, how will we compare them?

IBM suggest a way.
The last sentence is a great prediction. ;p

Xanadu helps create the Canada Quantum Network

Today’s encrypted networks will be at risk from quantum’s ability to break encryption protocols relying on the time taken to crack the prime numbers involved. QC can change this delay from years to hours. Networks are hard to create in Quantum as there is no “copy a qubit” capability in Quantum Computers (that exists in legacy computing). The Xanadu press release says access will be coming in 2021 to quantum secure communication.

Google’s claim of Quantum Supremacy & IBM’s reaction

In Nature, Google’s Quantum Supremacy paper, and IBM’s reply. And are we really comfortable with the term ‘supremacy’ given the racial overtones? Maybe ‘quantum advantage’ is better (even if it was rejected by John Preskill).

Forest – Easy, hybrid quantum programing

Presenters: W. Zeng, C. Osborn
Rigetti’s view of the QC world (from Quantum Information Processing 2018) gives a view of coding for QC from emulation to programming.

Forest – Easy, hybrid quantum programming

The Quantum Space Race

Presenters: Steve Martinis, Google

The Quantum Space Race

A Twitter Account Judging Quantum Reporting


Unsupervised Machine Learning on a Hybrid Quantum Computer

Machine learning techniques have led to broad adoption of a statistical model of computing. The statistical distributions natively available on quantum processors are a superset of those available classically. Harnessing this attribute has the potential to accelerate or otherwise improve machine learning relative to purely classical performance. A key challenge toward that goal is learning to hybridize classical computing resources and traditional learning techniques with the emerging capabilities of general purpose quantum processors. Here, we demonstrate such hybridization by training a 19-qubit gate model processor to solve a clustering problem, a foundational challenge in unsupervised learning. We use the quantum approximate optimization algorithm in conjunction with a gradient-free Bayesian optimization to train the quantum machine. This quantum/classical hybrid algorithm shows robustness to realistic noise, and we find evidence that classical optimization can be used to train around both coherent and incoherent imperfections.

Wanted Posted of Schrodingers Cat saying Wanted Dead AND Alive

Understanding quantum computers: The basics


Quantum.Tech Conference

Read two brief summaries from the September 2019 Quantum.Tech event in Boston, MA:

  1. A blog post written by Philipp Gerbert, of Boston Consulting Group (https://www.quantumtechcongress.co.uk/blog/impressions-from-quantumtech-2019)
  2. Report written by consulting firm TBR (https://www.quantumtechcongress.co.uk/downloads/tbrs-quantumtech-event-perspective).

Also, journey through the history of Quantum computing by one of the industry’s founding fathers, Seth Lloyd. You can access the video of Seth here.

Satellite-based entanglement distribution over 1200 kilometers


QC — Control quantum computing with unitary operators, interference & entanglement


Here’s what the quantum internet has in store


Someone trying to build a quantum computer at home


Quantum Computer Battle Royale: Upstart Ions Versus Old Guard Superconductors


Articles discussing Quantum Communication (especially QUESS):



This one has a nice formula for Schrödinger’s cat:


XKCD comic - Model of the Atom Over Time


Adiabatic – Wikipedia has you covered

Annealing – Quantum annealing (QA) is a metaheuristic for finding the global minimum of a given objective function over a given set of candidate solutions (candidate states), by a process using quantum fluctuations. (Yep, I am not fully understanding this one yet. Try this. Imagine a series of hills and valleys that you are looking at from the side in a 2D view. To see/read a point in successive valleys in classical computing, you would need to travel up and over the hill in between each one. In annealing, you can cut straight through the mountains to see/read the lowest valley immediately. Did that help? That’s not how it really works but it is sort of how it works.)

Ansatz – ?

Eigenstate – An eigenstate is the measured state of some object possessing quantifiable characteristics such as position, momentum, etc. The state being measured and described must be observable, and must have a definite value, called an eigenvalue. Wikipedia

Entanglement (Bell’s theorem refers to it as ‘non local’ connection) – once two qubits are entangled, they can be separated physically and somehow maintain a consistent state over long distances (this is the sort of stuff Einstein called ‘spooky action’ – so there’s that!)

Gates – the basis for logic and processing; think transistors in a microchip. N.B.: Each gate introduces noise, and once the noise reaches a certain level, the QUBITs are unreliable (decoherence) and the quantum superposition state must be recreated for further processing. (Noise and number of gates are critical metrics for monitoring QC.)

Hadamard (H) gate – one-qubit version of the quantum fourier transform

Hamiltonian – In quantum mechanics, a Hamiltonian is an operator corresponding to the sum of the kinetic energies plus the potential energies for all the particles in the system. Its spectrum is the set of possible outcomes when one measures the total energy of a system. Because of its close relation to the time-evolution of a system, it is of fundamental importance in most formulations of quantum theory.

Hilbert Space – a mathematical concept that is now an indispensable tool in quantum mechanics. The maths of QC occurs inside the Hilbert space.

Noisy intermediate-scale quantum computers (NISQ) – the name for the current state of the art QC’s – which is prototype-level and including error correction for up to 10 qubit

Photon – quantum particles of light

QPU – like a CPU but Quantum

qRAM – In qRAM, 40 qubits can store the same information as 1,000,000,000,000 legacy bits (that is 1012)

Quantum Approximate Optimization Algorithm (QAOA) – ?

Quantum Key Distribution (QKD) – works by sending photons across an optical link and designed to ensure that any attempt by an eavesdropper to observe the transmitted photons will perturb the transmission. Perturbation leads to transmission errors which can be detected by the legitimate users, thus verifying the security of the distributed keys. Note: As the key distribution rate of QKD is typically 1000 to 10,000 times lower than conventional optical communications; in practice, QKD is often combined with conventional symmetric encryption (e.g. AES) and used to frequently refresh short encryption keys. This is sufficient to provide quantum-safe security. This MIT article may help.

Quantum Noise – see gates. This is the wear on a qubit that comes from reading it.

Quantum supremacy – a future moment when quantum devices (without error correction) can perform a well-defined computational task beyond the capabilities of supercomputers. Given be the negative connotations of ‘supremacy’; maybe we could use ‘quantum advantage’ instead.

Qubit – like a bit but quantum (and thus significantly more powerful than classical bits as you combine multiple qubits.)

Superposition – the ability for a qubit to be both ‘0’ and ‘1’ simultaneously for processing (until actually read)

Variational circuits – define a set of classical routines which reference within their algorithm quantum circuits