quantum computing

1. A Tensor and vector product for Quantum

Hello, I am calculating the krauss operators to find the new density matrix after the interaction between environment and the qubit. My question is: Is there an operational order between matrix multiplication and tensor product? Because apparently author is first applying I on |0> and X on |0>...
2. A Random Quantum Walk

I am an undergraduate doing research on QC/QI. My current topic to learn is continuous-time quantum walks, but first I must learn the random quantum walk. That being said, I was wondering if someone could simply explain what a random quantum walk is and then explain how they could be useful with...
3. I "Basic" question about Grover's Quantum Computing algorithm

Hi everyone, I'm a computer scientist (not a physicist), so I will ask a computer scientist's question. In all the descriptions I found of Grover's algorithm, there is an element that is puzzling the computer scientist in me: it seems that you need to tell the Oracle about the position of the...
4. Can random, unguided processes produce a rational brain?

I am fascinated by Einstein’s quote that the most unbelievable aspect of the universe was that it was intelligible. So my question is does anyone know whether it is so unlikely as to be absurd to suppose that random unguided processes could produce a rational brain in man in as little as 3...
5. A How to measure the first qubit in two qubit system? QC

I was wondering how to measure the first or even the second qubit in a quantum computing system after for example a Hadamard Gate is applied to the system of these qubits: A|00>+B|01>+C|10>+D|11>? A mathematical and intuitive explanation would be nice, I am a undergraduate sophomore student...
6. I Oracle questions in Grover's Algorithm

Following these links: https://people.cs.umass.edu/~strubell/doc/quantum_tutorial.pdf https://www.codeproject.com/Articles/1131573/Grovers-Search-Algorithm-explained I have these questions: The Oracle "knows" the correct bits in the first invocation itself. So why do sqrt(N) invocations where...
7. I Clarification on what we can consider a qubit to be

In a 2 level quantum system, should I consider the states |0> and |1|> to be qubits by themselves? Or is only the SUPERPOSITION of these two states, \alpha |0> + \beta |1> considered to be a qubit?
8. I Quantum Computing and Superposition of states

I'm watching a lecture on the intro to quantum computing. See the attached image which will be useful as I describe my question. So the professor says that we have this single photon and it's in this state, $| 0 >$. He states that when we send this photon through a beam splitter that it...
9. What is Leakage in terms of quantum computing?

I am doing a project on stabilizer code, and I keep running into a term about qubits and leakage. What does leakage mean?
10. I Does 'Phase Inversion' grow exponentially?

Hi! So I'm studying Gover's Algorithm and I have this doubt: Does 'Phase inversion gate' grows exponentially? I mean, if I want to signal the one combination that is the answer, I must be able to represent all 2^N states, where N is the number of qubits in the system. How do I do this without...
11. A Shor's algorithm - need to uncompute auxiliary qubits?

Due to required reversibility, classical function (f(a)=y^a \mod N) in Shor's algorithm needs a lot of auxiliary qubits. I was afraid that their later treatment might influence the computation - and just got confirmation from Peter Shor himself: that we need to "uncompute" these auxiliary...
12. J

New member thread (Interested in Quantum Computing, AI)

Hey all, I'm a student in university who wants to Double Major in Computer Engineering and Physics or Mathematics. Ideally I want to get some time in working on quantum computers and some time in working on advanced AI, so one of the big things I want to do is pick the community's brain on...
13. Q

Physics Orienting myself toward quantum computing or a related field

I am well aware that QC-related graduate programs are competitive so I am preparing myself for a rejection. Not because I'm unconfident. But because everyone should have a backup plan just in case. I haven't applied yet because I'm about to take the GRE. I really do enjoy both quantum physics...
14. A Simple way to create entangled photon pairs?

Two photons arrive at a hypothetical 50:50 Beam-Splitter with no phase shift between reflected and transmitted modes. One enters the Left side and the other the Bottom side of the BS as shown in Fig.1 of the link below: https://drive.google.com/open?id=0B5JsDLKoUSA5emk5Qk9nUHVIelE Each photon...
15. I Arithmetic Block in Shor Algorithm

Hello everyone! So I was looking at Shor Algorithm for prime factorization and I have some doubts in the arithmetic part. Let's define a function f that : f(x) = ax mod N. The middle step in shor algorithm is to calculate, simultaneously, all values of f. In some papers and books, I saw some...
16. A What's the best quantum simulator?

Hello. What is the best quantum simulator till now? We could select two categories: a) Best full simulator able to solve the equations describing a system in 3D and watching its temporal evolution. b) Best digital simulator, algorithm analyzer. For the second options I have some candidates...
17. Books on quantum computing?

Hello. What is a good book to learn Quantum Computing? I've being looking for the most common ones and reading some reviews at Amazon, and created this list: A Short Introduction to Quantum Information and Quantum Computation, Le Bellac, 2006 An Introduction to Quantum Computing Algorithms...
18. Physics Simulation and model science or quantum computing

I am a computer science under graduate,I am more interested in scientific research, so I am preparing to enrol myself masters in quantum computing or simulation sciences. before i join i want to research what are the scope and job opportunities are available for simulation sciences(like...
19. I Help in understanding a quantum circuit

I'm in a proyect to simulate quantum circuits in robots like in this paper ( http://ieeexplore.ieee.org/document/4215941/ ) ,the first thing that i need to do is to simulated the circuit that is in that paper: But i'm having trouble understanding how the hadamard gate affects the "C"...
20. Programs Choosing a Master's degree in Physics

I am a physics student from Spain and hopefully I will be finishing my degree in physics (4y) by next June. I am trying to decide on a Master's program to study but I am finding very difficult to decide since there are so many oportunities and so diverse specially when looking for programs...
21. I Simon's Algorithm

Hi all, I am sure some of you have heard of Simon's algorithm that calculates a secret string s when given a black box. Basically, let's say we have a qubit x that is n digits long. Now the black box contains a function f that outputs f(x+s) where s is the mystery string and + is bit-wise modulo...
22. I How reduced density matrix obtained from the matrix.

Can any expert help me in explaining how this example below get the reduced density matrix from the density matrix in bipartite system. \rho =\frac{1}{4}\begin{pmatrix} 1 & 1 & cos(\frac{\alpha}{2})-sin(\frac{\alpha}{2}) & cos(\frac{\alpha}{2})+sin(\frac{\alpha}{2}) \\ 1 & 1 &...
23. Research in Quantum Computing

Hi, I am an undergraduate student from India. Pursuing double major in Physics and Mechanical Engineering. I have completed 4 semesters(2 years) of my college. I had taken a class titled "Quantum information and computing" and it interested me a lot. I really love math and computations...
24. E

Hopefully an Interesting Introduction

Hey Everyone! I'm new here as a member but not as a visitor. I've looked upon these forums for answers, guidance, and general informative information. I liked what I saw so much that I decided to join. A little about me: My name is Edward, I live in Tennessee and am currently working my way...
25. Quantum Computing

Hello, Am an undergraduate student of physics(hons) and want to work on Quantum Computing in future. Can anybody please suggest how I should go about it? Thanks in advance
26. A What is quantum computing research mostly focused on?

What is quantum computing research mostly focused on? I mean, is it mostly about a physical point of view ( Like building better quantum transistor, or better quantum diodes, or, for example, using entalgment effect, to achieve better purposes), or is it mostly focused with quantum architectures...
27. Greetings to all

I am not from physics but computer science. I am interested in the prospect of quantum computing in the future and would like eventually to learn a little bit about issues of hardware realizations of quantum computing from experts of this forum.
28. Is quantum programming really possible?

Hello all, I have come here to gather what the communities view is on the possibility of quantum computing in relation to the actual logic behind synchronous programming and the laws that (seem to) govern the quantum realm. Coming from a background in computer science, I have studied the basic...
29. Schools Chances of Getting Into Graduate School Ph.D Programs

I am a rising senior at a small liberal arts college, with an incredibly small (and therefore unrecognized) physics program. I am seeking advice regarding which Ph.D programs are within my reach. I plan on applying to AMO (Atomic, Molecular, and Optics) Ph.D programs with the intention of...
30. Measuring a qbit

I am newly learning quantum computing and am confused about some concepts. Suppose your qbit is the electron of a hydrogen atom and its in the state α|0> + β|1> . As far as I can understand, this means that if you measure the qbit in |0>, |1> basis, you will get a ground state electron with the...