Most Popular
1500 questions
9
votes
3 answers
Is it important for a quantum computer to be shielded by the magnetic field?
I've been browsing The D-Wave 2000Q site when I bumped into this aspect of their quantum computers:
A Unique Processor Environment
Shielded to 50,000× less than Earth’s magnetic field
Why is that relevant? What would happen if it would be much…
Adelin
- 305
- 2
- 12
9
votes
1 answer
What is known about quantum algorithms for graph isomorphism?
Shor's algorithm (for factoring integers) and Grover's algorithm (for searches) are the two most well-known quantum algorithms. I was wondering if there was a similar result in QC that dealt with the Graph Isomorphism problem?
I can't seem to find a…
paulinho
- 251
- 1
- 4
9
votes
1 answer
How to create an arbitrary state in QISKit for a local_qasm_simulator?
I would like to play with a quantum circuit local_qasm_simulator in QISKit, but I do not want to implement a separate quantum circuit that would prepare an initial state.
The way I do it now is by falling back to NumPy. Specifically, first, I…
Alexander Pozdneev
- 441
- 4
- 10
9
votes
2 answers
How to get state vector from QasmSimulator in Qiskit
I'm currently able to get state vector in Qiskit using state_vector backend using something like :
backend = Aer.get_backend('statevector_simulator')
job = execute(qc, backend=backend, shots=1, memory=True)
job_result =…
user12910
- 471
- 1
- 4
- 9
9
votes
1 answer
Impact of ordering Hamiltonian terms for Trotterization
In Trotterization, the typical Hamiltonian considered is:
$$ H = \sum_{p, q} h_{pq} a^{\dagger}_p a_q + \sum_{p, q, r, s} a^{\dagger}_p a^{\dagger}_q a_r a_s $$
Which is then converted into a sequence of gates by the Jordan Wigner…
C. Kang
- 1,847
- 9
- 24
9
votes
1 answer
Is there any 'official' list of errata for Nielsen & Chuang?
The book Quantum Computing and Quantum Information by Nielsen and Chuang is a well-known and celebrated text book that can act as a resource in a wide variety of topics. Of course, in such a vast textbook there might arise small errors.
Its own…
JSdJ
- 5,819
- 15
- 36
9
votes
1 answer
Consequences of $MIP^\ast=RE$ Regarding Quantum Algorithms
The (pending-peer review) proof of $MIP^\ast=RE$ in this pre-print has been hailed as a significant breakthrough. The significance of this result is addressed by Henry Yuen (one of the authors) in this blog post. Scott Aaronson also lists some of…
Jonathan Trousdale
- 3,452
- 9
- 20
9
votes
2 answers
Preparing any superposition of fixed Hamming weight states
There exists a nice way of preparing any superposition (with real amplitudes — this is the case I'm interested in) of states $\{\ldots0001\rangle,\,|\ldots0010\rangle,\,|\ldots0100\rangle,\ldots\}$, etc. This can be achieved with an $O(\log_2…
mavzolej
- 2,271
- 9
- 18
9
votes
3 answers
What does quantum gate fidelity mean?
The formal definition states that it's the distance between two quantum states. What does that mean experimentally? Does distance here mean the distance between two states on the Bloch Sphere? I am a little confused about the meaning of gate…
Maxx
- 171
- 1
- 4
9
votes
2 answers
Can quantum computers be used to solve P = NP
The P versus NP problem is a major unsolved problem in computer science. It asks whether every problem whose solution can be quickly verified can also be solved quickly. It is one of the seven Millennium Prize Problems selected by the Clay…
Peter Morgan
- 199
- 5
9
votes
2 answers
How to explain in layman’s terms the significance of the difference of qubits of the D-Wave and IBM QX?
So, @AndrewO mentioned recently that he has had 'encounters' with people wondering why D-Wave has a lot more qubits than IBM. Of course, this comparison is faulty, since the IBM and D-Wave's machine may both exploit quantum effects to a certain…
Discrete lizard
- 3,154
- 2
- 20
- 42
9
votes
1 answer
Hadamard Overlap Test
I am trying to understand a test called Hadamard Overlap Test, which consists of a destructive swap test (section IV of swap test and Hong-Ou-Mandel effect are equivalent) right after a Hadamard test. The circuit is from the Variational Quantum…
Enrico
- 493
- 2
- 12
9
votes
1 answer
How to decide which quantum device to use if a quantum algorithm is given?
I'm planning to write my master thesis in quantum computing. The subject of the thesis is to find out which attributes (properties, features) of quantum algorithms respectively their implementations (circuits) are important to decide which quantum…
krsp
- 99
- 1
9
votes
1 answer
Correct formulation of Exercise 4.11 in Nielsen and Chuang
Inspired by the comments in this question, there is the errata for question 4.11 pg 176 in Nielsen and Chuang. The original form states that for any non parallel $m$ and $n$, then for an arbitrary $U$:
$$U = …
Sam Palmer
- 1,009
- 5
- 12
9
votes
1 answer
Explain the representation of the CNOT gate in ZX-calculus
In ZX-calculus, the CNOT gate is represented by this:
Can someone show me why this is true, using just the basic rewriting rules? All books/papers I have seen simply take it without proof, but I can't see why it is true.
NNN
- 403
- 2
- 10