r/QuantumComputing

Hello, I have online assessments to take for Optiver's Kickstart Trading Program in Amsterdam. Do you have any advice on how I can take them, please? Thank you very much for the help 😊

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Hello ,

Has anyone recieved the QGSS 2026 completion certificate and the badge?

Also the QDC application results?

I made a short whiteboard video explaining density matrices from the ground up, focusing on the linear algebra behind them: pure vs. mixed states, diagonal vs. off-diagonal entries, coherence, projectors, and how measurement probabilities arise from the matrix representation.

Sharing in case it’s useful to anyone interested in how linear algebra shows up in quantum mechanics. Corrections or additional insight are always welcome.

Howdy! Anyone attending IEEE Quantum Week 2026 (QCE26) in Toronto, Ontario, Canada, from September 13–18, 2026 . Just checking if anyone is also planning to go, would be great to connect. Drop a comment or DM.

I have recently started learning about and working with the QIR LLVM extension by Microsoft and others.
As far as I know, Microsoft and Quantinuum are the only companies that officially use QIR for their quantum computers.

They both have cloud services in Microsoft Azure Quantum and Quantinuum Nexus. They seem to have advanced simulators and optimisation tools.

My question is, if any of you have ever used these?
I would be interested in your experience and thoughts about them.

Weekly Thread dedicated to all your career, job, education, and basic questions related to our field. Whether you're exploring potential career paths, looking for job hunting tips, curious about educational opportunities, or have questions that you felt were too basic to ask elsewhere, this is the perfect place for you.

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• Careers: Discussions on career paths within the field, including insights into various roles, advice for career advancement, transitioning between different sectors or industries, and sharing personal career experiences. Tips on resume building, interview preparation, and how to effectively network can also be part of the conversation.
• Education: Information and questions about educational programs related to the field, including undergraduate and graduate degrees, certificates, online courses, and workshops. Advice on selecting the right program, application tips, and sharing experiences from different educational institutions.
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• Basic Questions: A safe space for asking foundational questions about concepts, theories, or practices within the field that you might be hesitant to ask elsewhere. This is an opportunity for beginners to learn and for seasoned professionals to share their knowledge in an accessible way.

Grover's algorithm is one of the most famous quantum protocols ever developed, providing a quadratic speedup over classical approaches for the search problem. Unlike most quantum algorithms, Grover's algorithm is unique in that its applications are quite ubiquitous, as any classical algorithm that uses some kind of unstructured search can always be sped up using this procedure, even if the advantage gleaned is not as significant as it is for something like Shor's algorithm (assuming factoring is classically hard ofc). In this video, I derive the algorithm from geometric intuition and then demonstrate its optimality in terms of query complexity.

hey, i made a new video working through a proof involving the reduced resolvent and why the spectral gap matters so much in adiabatic quantum computing. the main idea is that the reduced resolvent has this inverse-gap behavior, roughly 1/Δ, so as the spectral gap gets smaller the resolvent norm grows and the error bound can get much worse.i go through the proof step by step and explain what the resolvent, spectral projections and operator norms are along the way, so hopefully it’s useful even if you haven’t seen all of the notation before.

Earlier this year the two largest superconducting QC players (IBM and Google) signalled they might be diversifying away from superconducting - Google with the announcement that they're creating a new neutral atom capability and IBM with their acquisition of silicon spin capability in HRL.

I'd be interested in people's views on whether we should take from this that superconducting has no path to scaling, or if one could foresee heterogeneous quantum computing systems that leverage the respective strengths of multiple modalities for different applications?

I was working through this proof and thought it was a really interesting way to introduce some of the algebra behind quantum error correction. I go through why QEC syndromes add modulo 2 and why the syndrome map is a homomorphism from the Pauli group into a binary vector space.

Along the way I also cover stabilizer generators, F₂, zero syndromes, the kernel and normalizer, and briefly connect the ideas to surface codes and decoding.

If you’re newer to quantum error correction, I tried to build everything from the ground up and explain the notation before getting into the proof. Would love any feedback or discussion.

I’m about to start my MS Thesis (enrolled in MS(Al)

In last semester I studied reinforcement learning and I want to do something which combines a both the reinforcement learning and quantum computing

If any of you have a good idea or any experience do let me know as in my institution there aren’t anyone with quantum computing knowledge

Hey! I was working through a proof showing that each subsystem of the quantum singlet state has zero local spin expectation in every direction.

While going through it, I realized how much of the proof is really linear algebra underneath the quantum notation. So I took my time explaining the eigenvalues and eigenvectors, unit vectors, Pauli operators, tensor products, inner products, and expectation values behind the calculation.

If you're learning linear algebra and want to see how these concepts show up in quantum mechanics, I hope this helps!

Microsoft's quantum vice president's interesting take: "This notion of having peer reviews and publications doesn't work in this fast-moving world right now. This paper thing is kind of boring now."

I keep hearing that quantum computers could eventually break passwords or defeat current cryptographic systems. But there's something about this that I don't fully understand.

Let's say an attacker doesn't have access to the password database or the stored password hashes. They only have access to the actual login system, where they can submit a password and the server tells them whether it's correct or not.

A quantum computer might be able to search through a huge number of possible passwords much faster than a classical computer. But wouldn't the attacker still need to have each candidate password verified by the server?

In other words:

Quantum computer: generates/searches possible passwords extremely quickly
↓
Classical server: checks whether each password is correct

Wouldn't the classical server (and things like rate limiting, network latency, account lockouts, etc.) become the actual bottleneck?

Also, I understand that this is different if the attacker has stolen the database and has the password hashes. In that case, they can perform an offline attack and potentially implement the verification function as part of a quantum algorithm, without asking the real server for every guess.

So my question is specifically about the online attack scenario:

If the attacker only has access to a login/verification endpoint, how would a quantum computer actually provide an advantage? Can a quantum algorithm somehow perform the verification without having direct access to the server for every candidate, or would the classical server fundamentally limit the speed of the attack?

I'm trying to understand where my intuition is wrong here.

I will soon, after finishing mg PhD in europe, start an R&D scientist role (Quantum Computing) in a company in europe. I want to know how people on reddit have leveled up in the corporate sector of this niche segment of scientists? I am not an academia kinda person so industrial Research is my calling, but I am also really interested in managing projects and going all the way upto a CTO or even CEO, how do you do that? I need tips and tricks, both general and specific to R and D of any science-based roles. Thanks :)

The Riemann hypothesis claims that the locations of prime numbers along the infinite number line all adhere to a beautiful and orderly, but obscure formula. Yet 167 years after German mathematician Bernhard Riemann made this guess, and in spite of a million-dollar bounty, mathematicians still have no idea how to prove it. Now a team in China has managed to encode that formula into a physical system and explore its workings using a quantum computer.

Weekly Thread dedicated to all your career, job, education, and basic questions related to our field. Whether you're exploring potential career paths, looking for job hunting tips, curious about educational opportunities, or have questions that you felt were too basic to ask elsewhere, this is the perfect place for you.

​

• Careers: Discussions on career paths within the field, including insights into various roles, advice for career advancement, transitioning between different sectors or industries, and sharing personal career experiences. Tips on resume building, interview preparation, and how to effectively network can also be part of the conversation.
• Education: Information and questions about educational programs related to the field, including undergraduate and graduate degrees, certificates, online courses, and workshops. Advice on selecting the right program, application tips, and sharing experiences from different educational institutions.
• Textbook Recommendations: Requests and suggestions for textbooks and other learning resources covering specific topics within the field. This can include both foundational texts for beginners and advanced materials for those looking to deepen their expertise. Reviews or comparisons of textbooks can also be shared to help others make informed decisions.
• Basic Questions: A safe space for asking foundational questions about concepts, theories, or practices within the field that you might be hesitant to ask elsewhere. This is an opportunity for beginners to learn and for seasoned professionals to share their knowledge in an accessible way.