Unanswered Questions
520 questions with no answers
13
votes
0
answers
308
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Is HHL still BQP-complete when the matrix entries are only in {0,1}?
I'm studying BQP-completeness proofs of a number of interesting problems of Janzing and Wocjan, and Wocjan and Zhang. Janzing and Wocjan show that estimating entries of matrix powers $(A^m)_{ij}$ with ...
- 12.4k
7
votes
0
answers
352
views
Solving linear system $Ax=b$ with exponential speed-up via binary optimization?
The main disadvantage of HHL algorithm for solving $A|x\rangle = |b\rangle$ is that exponential speed-up is reached only in case we are interested in value $\langle x|M|x\rangle$, where $M$ is a ...
- 1
7
votes
0
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210
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Run VQE for parametrized quantum circuit with ancilla qubits
Let's say we have the following circuit (picture and code shown below), and now the $q_0$ is an ancilla qubit. If the system of interest has only two qubits, Is there a way to use only $q_{1,2}$ as my ...
glS♦
- 26.9k
6
votes
0
answers
278
views
Quantum State Tomography Implementation in IBMQ
I am working to understand quantum state tomography, specifically using the algorithm presented in PRL 108, 070502. This paper is referenced in IBMQ implementations of QST, both in old deprecated ...
6
votes
0
answers
132
views
Writing circuits in Qiskit using only Clifford and T gates
Is there a way in Qiskit to write my circuit using only Clifford and T gates (CX, S, H, T and I think also $S^\dagger$ and $T^\dagger$)? With the function compile (with aer simulator) it gives me some ...
- 3,469
6
votes
0
answers
132
views
What is the largest linear system of equations solved using HHL experimentally?
Can someone tell what is the largest system of equations solved using HHL algorithm experimentally?
I know the $8$ x $8$ system has been solved experimentally. Has someone gone beyond this to solve $...
- 2,965
6
votes
0
answers
141
views
Bell State 11 not working for parity curve
I am currently writing a script to automate the creation of parity curves for a 2 qubit bell state and then calculate fidelity and proving entanglement from that (inspired by this paper). It was going ...
glS♦
- 26.9k
6
votes
0
answers
151
views
How exactly is the stated composite state of the two registers being produced using the $R_{zz}$ controlled rotations?
This is a sequel to How are two different registers being used as "control"?
I found the following quantum circuit given in Fig 5 (page 6) of the same paper i.e. Quantum Circuit Design for ...
- 17.8k
5
votes
0
answers
271
views
How to get the compiled circuits and measurements from a Qiskit Runtime job
I have not been able to find any way to retrieve the compiled circuits and the measurement counts used for a Qiskit Runtime job. This page describes the various error suppression mechanisms available. ...
- 726
5
votes
0
answers
662
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Add noise_model when using 'ibmq_qasm_simulator' backend and provider.runtime.run() function
I am trying to test some qiskit code that employs readout-error mitigation using the ibmq_qasm_simulator backend and Qiskit Runtime. I am getting the backend as ...
- 51
5
votes
0
answers
71
views
In the HHL algorithm, how large should the eigenvalue estimation register be?
In the HHL algorithm, we need to estimate the eigenvalues of a matrix $A$. The result is stored in a register with $l$ qubits. Let $T = 2^l$. $T$ cannot be too small, otherwise the result would have a ...
glS♦
- 26.9k
5
votes
0
answers
725
views
OpenFermion to Qiskit
Is there a direct way to go from an object generated in OpenFermion to objects usable in Qiskit? I can't find anything about any plugin.
It's not too hard to translate into pyQuil and then to Qiskit ...
5
votes
0
answers
160
views
Results from looped experiments on IBM Q different than individual experiments
I'm experiencing an issue while using Qiskit where the counts from a job return vastly different values when ran in a loop or as an array of circuits as opposed to single experiments when run by ...
- 17.8k
5
votes
0
answers
157
views
How can I express controlled unitary operation in QPE of this implementation of HHL?
I have found this implementation of HHL, and I don't understand why the controlled unitary operation is expressed in the form of $\exp(i t_0 A/2)$ and $\exp(i t_0 A/4)$.
The rotation of $\pi$ and $\...
- 17.8k
5
votes
0
answers
135
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Why is there no $N$ in the time complexity of the QLSP algorithm by Childs et al.?
The paper Quantum linear systems algorithms: a primer by Dervovic et al has this table on page 3:
I'm not sure why there's no $N$ in the time complexity of the algorithm by Childs et al. i.e. $\...
- 17.8k