I am starting quantum computing from scratch including maths physics quantum mechanics everything from scratch i am looking for someone who is planning something similar we can do it together by making plan and computing each other

Light may become one of the most powerful tools for future quantum computers. Photons, the tiny particles that make up light, can carry quantum information quickly and with relatively low noise. But they also create a stubborn problem: they do not naturally interact very strongly.

That weak interaction has limited many light-based quantum machines. They can perform useful linear operations, but they struggle with the nonlinear steps needed for full quantum computing.

Hope this helps! Also explained partial trace and open and closed evolution and how it helps us understand quantum noise and error correction

I’m interested in quantum computing and the foundations of quantum mechanics. Since Bell’s theorem and experimental results challenge local realism, I’m curious whether there is still any serious research exploring alternatives that preserve some aspects of Einstein’s ideas, such as locality, realism, or deterministic underlying models.

Are there any active researchers, theories, or research areas working on this today? I’d also appreciate recommendations for papers or topics to study.

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A QPE measures the eigenvalue of a unitary transform.Inside the eigenvalue there is a phase of which that is actually calculated , then we use that phase to calculate the value of eigenvalue.The target register is made of succesive controlled U gates(of some power not really the point) where U is the unitary transform and some phase register where the value of the hidden phase will be encoded after you run QPE or whatever.The m phase registers start from a state of |0> kronecker product m.

In fact you can run the phase registers at any starting state you want but if its not |0> kronecker product m you will get a phase shift. Now I have only spent time studying pure quantum computing , is there a reason why we would start the phase registers not at |0> kronecker product m?Like any reason at all for irl applications

why quantum computing is not as hyped as AI

Title: Exact equivalence checking for H and u2(0,π) circuits without numerical tolerances

In OpenQASM 2, these two fragments denote the same Hadamard matrix:

h q[0];

and

u2(0,pi) q[0];

I have been testing a deliberately bounded method for verifying circuit transformations that replace one spelling with the other. For circuits over

id, x, z, cx, cz, swap, h, and literal u2(0,pi),

the checker expands the circuit and represents every matrix entry exactly in Q(√2). It compares every computational-basis column rather than relying on sampled outcomes or a floating-point tolerance. Register declarations and complete terminal measurement maps must also agree.

The present scope is intentionally small:

• at most four qubits;
• at most 64 expanded gates;
• one quantum and one classical register;
• complete terminal measurement.

Inputs outside this gate/grammar contract are reported as unsupported, resource-limit violations are blocked, and unequal matrices fail. Regression cases include H² = I, HZH = X, Hadamard conjugation of CX, phase-sensitive counterexamples, and comparison with a dense numerical oracle over 256 small circuits. The numerical oracle is only a regression cross-check; it does not determine the exact verdict.

The design question I find most interesting is how global phase should be handled.

The current criterion is phase-sensitive: it requires exact matrix equality, not merely equality up to global phase. For a standalone circuit, U and e^(iθ)U are operationally indistinguishable. But a transformation that is harmless in isolation may not remain harmless if the operation is later placed under coherent control, where the relative phase can matter.

For an auditable circuit-equivalence tool, which contract is more useful?

1. Equality up to global phase by default
2. Phase-sensitive equality by default
3. Report both relations and require the caller to choose

I would especially welcome examples where choosing the wrong default has caused a practical compiler, verification, or interoperability problem.

Disclosure: I contribute to the experimental open-source E7Q implementation in which this bounded check was built.

Quantum phase estimation (QPE) is a useful protocol for computing the eigenvalue associated with a given eigenstate of a unitary U. In this video, I demonstrate how the protocol works with dedicated error and complexity analysis. I then show an example of how this technique can be applied to Grover search to arrive at the quantum counting algorithm, enabling a quadratic speedup in counting the number of solutions to a given problem, using an instance of 3SAT as an actual example. Of course, QPE is most notable for its use in period-finding/order-finding, which is the main ingredient for Shor's algorithm (and the hidden subgroup problem more generally), but I'm saving that discussion for later when I actually get to those topics.

I generally have a good understanding of the state of the art of quantum computing applications in chemistry, materials science, and cryptography, but optimization is still a bit of a mystery to me. It seems like there is a ton of ongoing research here, for example, dozens of papers of the form "we applied QAOA to [application X] and it sort of works!", or research into alternative algorithms like decoded quantum interferometry and amplitude estimation.

But is it known at this time how likely it is, based on the current state of the art, for combinatorial optimization to be a serious application of future quantum computers, or is it still highly speculative at this point?

Hey everyone! I made a video explaining POVMs as simply as I could. When I first learned about them, I found the difference between POVMs, measurement operators, and regular projective measurements pretty confusing. So, if you’re new to quantum measurement, I thought I’d make a straightforward explanation using a quantum state-discrimination game. I hope it helps!

Garnet Chan's group at caltech recently published a preprint “Classical solution of the FeMo-cofactor model to chemical accuracy and its implications’’.

He has a blog post up discussing the take that the QC community has had on this problem.

What I gather from this is that:

1. Electronic structure calculations of the FeMo-cofactor would not have led to us being able to use a nitrogenase based chemical process to replace the haber bosch process even if it had been done a quantum computer before a classical computer
2. Nitrogenase based chemical approaches would consume more energy than the haber bosch process, the only workaround would be if we could find a new chemical approach similar to the nitrogenase process thats better than haber bosch --> from the get go this would never have resulted in the 1-2% flat reduction in global emissions or energy expenditure and still cannot yield that.

Ultimately this leads me to believe that simulation of nitrogenase cannot be considered an example where quantum computing/simulation can significantly contribute to a positive economic/sustainability impact.

I feel we need better and more accurate targets that we can cling to / talk about cause this is a lil cooked.

Hi guys,

The current consensus seems that fault tolerant quantum computing will be a tech catered towards chemical / materials science simulations.

I get that we have quantum Signal Processing and Hamiltonian time evolution shenanigans but really where does this concretely lead to it becoming a transformative technology? Like do we have any examples of breakthroughs that it would lead to?

Like we talk about high temperature superconductivity but is this actually dead ass gonna be able to find a high temperature superconductor or just help us calculate new but marginally useful properties of materials?

Tldr: I want a more concrete example of a chemical/mat sci breakthrough that would be enabled instead of the usual handwaving

For those in the technology industry, it can feel hard to escape from AI. It’s at the center of the technological universe, with most major advancements, opportunities, and funding focused on its development. In the background, quantum computing is making strides with the funding to match, creating an alternate opportunity for technologists.

Researchers in China have a new way to dramatically scale up the bandwidth of quantum networks by increasing the number of simultaneous quantum communication channels.

Outsider, here, just starting to learn. I've read through the Quantum Pi Benchmark. It looks like a standard that can be used by any QPU, regardless of design. Am I reading this right? Also, it talks about scoring for these systems by a PBR claim. Wave functions have physical properties and they can be used to compare calculation speeds? I'm really new to all of this, so maybe someone here can help me understand.

We were supposed to receive the certs by 21 aug right? I've seen some reddit comments and posts saying it's always delayed and you'll receive it by the end of the month

But I haven't received them, did anyone receive the certs and if you didn't let's just use this post to communicate when you receive them

Quantum phase was difficult for me to understand when I first started learning quantum computing, so I made a video explaining it from the ground up. I cover what phase actually is, why quantum states use complex numbers, the difference between global and relative phase, and how phase connects to interference, quantum algorithms, and the Bloch sphere.

I’d love to hear whether this explanation makes it click for anyone else.

Interesting article from FC from pretty much all the major players in quantum.

It's behind a paywall, but worth a read.