Questions tagged [nisq]

For questions related to Noisy Intermediate Scale Quantum (NISQ) computing. NISQ computers cannot be classically simulated in a reasonable time but are not advanced enough to also be error corrected.

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Can Wiesner's quantum money be realized (with logical qubits) today?

Consider Wiesner's quantum money scheme. With today's devices and today's error correction and mitigation schemes, how long can we hold $n$ logical qubits such that they are all (logically) in a ...
Mark Spinelli's user avatar
5 votes
1 answer
266 views

Qudits in NISQ Devices: Benefits Beyond Dimensional Advantages?

It's clear from foundational research that qudits can provide an enhanced control of the Hilbert space over qubits, and I've encountered references that highlight improved robustness and noise ...
banercat's user avatar
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7 votes
3 answers
657 views

Does Google's error correction paper invalidate Gil Kalai's arguments?

In his paper "The Argument against Quantum Computers, the Quantum Laws of Nature, and Google’s Supremacy Claims", Gil Kalai argues that quantum advantage will never be reached. For NISQ ...
Tristan Nemoz's user avatar
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7 votes
1 answer
274 views

Publicly available samples for quantum circuits and/or simulators

With Yosi Rinott and Tomer Shoham we studied various statistical aspects of samples coming from NISQ computers. My question is about available data consisting of samples from NISQ computers We would ...
Gil Kalai's user avatar
  • 201
1 vote
0 answers
28 views

Combine qubits together to get additonal accuracy

The Peres-Mermin Magic Squares game at https://en.wikipedia.org/wiki/Quantum_pseudo-telepathy defines a simple circuit that outputs legal winning game outcomes. An "ad-hoc" circuit that does ...
Anna Naden's user avatar
5 votes
2 answers
257 views

Can we use cryptocurrency mining to verify claims of quantum advantage?

Beginning with the earlier works of work of Brakerski et al. or the more recent results of Kahanamoku-Meyer et al., interactive proofs of quantum advantage entail a classical verifier (Vicky) ...
Mark Spinelli's user avatar
2 votes
1 answer
62 views

Can ancilla-based parity measurements be used to detect errors in NISQ algorithms?

Measuring stabilizer eigenvalues is a fundamental part of quantum error correction. However, I was wondering if the idea of measuring a stabilizer using an ancilla could be useful in other contexts as ...
Lior's user avatar
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8 votes
2 answers
269 views

What use cases are there for 127 qubit QPUs?

IBM have recently announced their 127 qubit Eagle processor. Other approaches, such as Rydberg arrays, have now 256 qubits, as for example in QuEra's QPU QPU. While these are without a doubt ...
Lior's user avatar
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1 vote
2 answers
73 views

Is it possible to efficiently measure outer products of quantum states, of the form $|a\rangle\langle b|$?

I am looking at a matrix reconstruction algorithm that, given singular values $\sigma_i$ and quantum states $|u_i\rangle$ and $|v_i\rangle$ that are efficiently prepared on a quantum computer, ...
JoJo's user avatar
  • 99
6 votes
0 answers
274 views

Could the Hamiltonian of a 2x2 Rubik's Cube be simulated with a NISQ device?

Consider the four cells on each of the six faces of the 2x2x2 Rubik's cube (the pocket cube). We can construct and simulate a quarter-turn Hamiltonian as below. $^*$ Let $\langle F_1,U_1,R_1\rangle$ ...
Mark Spinelli's user avatar
2 votes
1 answer
90 views

Mahadev's classical homomorphic encryption for quantum circuits and NISQ computing

I'm currently reading Mahadev's paper Classical Homomorphic Encryption for Quantum Circuits: https://arxiv.org/abs/1708.02130 I was told that Mahadev's scheme is not something that can be implemented ...
Haim's user avatar
  • 257
2 votes
0 answers
63 views

How do you quantify the figurative 'cost' of a quantum circuit

Many gates are not available on a real computer and therefore the circuit must be transpiled into a specific set of gates. I have seen this equation below which is used to to determine the 'cost' of a ...
John's user avatar
  • 107
8 votes
0 answers
299 views

Definition of a NISQ device with respect to qubit counts and error rates

How do we define whether a device is a noisy intermediate-scale quantum (NISQ) device with respect to number of qubits and their error rates? Does it make sense to do this? I believe I once saw a ...
Greenstick's user avatar
  • 1,076
3 votes
1 answer
139 views

What is the "quantum mean value problem"?

What is the "Quantum mean value problem"? A definition I found was that it is "estimating the expected value of the tensor product observable on the output state of a quantum circuit&...
chois3's user avatar
  • 167
2 votes
1 answer
132 views

Design NISQ Circuit with StrawberryFields

I am trying to design this circuits with strawberry fields. However I could not connect my first and second qubit mode: orange boxes are beam splitters, blue boxes are phase shifters. The green box ...
quest's user avatar
  • 636
1 vote
2 answers
126 views

What are the libararies for Machine Learning on NISQ Chip? And What are the roadmaps?

Nowadays quantum learning is hiring. And we can see mainly two different area. One of them is variational algorithms part. And the other one is classical learning for quantum systems like NISQ. (Some ...
quest's user avatar
  • 636
2 votes
2 answers
227 views

Quantum Machine Learning in NISQ era

I know that quantum algorithms can be useful for machine learning ("ML") methods, and vice versa. For example if we use QAOA we can use for the optimization part different types of ML ...
Jeff24's user avatar
  • 141
4 votes
2 answers
252 views

Gate SWAP vs Physical SWAP in Trapped Ions for chain reordering

In trapped ion quantum computers, especially in systems with multiple traps, you may need at some point to perform a "chain reordering", in which you change an ion's position within the ion ...
faysay's user avatar
  • 41
3 votes
1 answer
63 views

NISQ algorithm: do they all have circuit updated between each run AND impossible to predict when they will stop?

I don't know very much the NISQ algorithms, but the ones that I know are based on kind of "Hybrid" calculation between a quantum computer and a classical computer. Indeed, for instance in ...
Marco Fellous-Asiani's user avatar
1 vote
1 answer
123 views

Why is the VQE insensitive to noise?

I was going through the Grove documentation on the Variational Quantum Eigensolver. In one of the demonstrations with noisy gates, it is seen that resulting eigenvalue is quite close to the expected ...
bhq's user avatar
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3 votes
1 answer
154 views

What is the implication of locality in QAOA?

Suppose I am solving the TSP formulated as a QUBO problem using QAOA. I understand from the original paper that there is a parameter $p$ which sets the number of steps used in the alternating ansatz. ...
Alexander Soare's user avatar
3 votes
1 answer
191 views

How is back-propagation done in "Transfer learning in hybrid classical-quantum neural networks"

Just read this paper from Xanadu on Quantum Transfer Learning and a couple of things are unclear to me regarding the optimisation step. How is back-propagation done through the classical weights ...
Alexander Soare's user avatar
7 votes
1 answer
523 views

What's the point of VQE if classical computers can solve for eigenvalues easily?

From a few VQE tutorials online I see that they normally start with something like: VQE is a way of getting a good estimate for the upper bound of the ground state of a quantum system's Hamiltonian....
Alexander Soare's user avatar
2 votes
1 answer
231 views

Will NISQ based algorithms be useful in fault-tolerant Quantum computers?

As a data scientist, I want to use the cutting edge algorithms of machine learning to build my models, I am interested in quantum machine learning, the recent research in QML is about variational ...
Carlos Alfredo Vergara Rojas's user avatar
2 votes
0 answers
48 views

Dealing with noise in NISQ

I wanted to know if there are some way in NISQ (we run "bare" gate without Q.E.C) to certify if an algorithm will give a correct or wrong answer based on the process of a single gate ? For example in ...
Marco Fellous-Asiani's user avatar
8 votes
0 answers
538 views

What are the "nice" properties of the diamond norm and why is it used?

I have heard about the diamond norm, and from what I understood it is a "nice" tool to quantify quality of quantum gates in the NISQ era. I would like to know a little more before going in detail in ...
Marco Fellous-Asiani's user avatar
4 votes
1 answer
735 views

Quantum speedup in Bayesian machine learning on NISQ computers

It is well known that in Bayesian learning, applying Bayes' theorem requires knowledge on how the data is distributed, and this usually requires either expensive integrals or some sampling mechanism, ...
Carlos Alfredo Vergara Rojas's user avatar
7 votes
3 answers
3k views

Pennylane and Qiskit for quantum machine learning

I'm interested in quantum computing, specifically in “quantum machine learning” (QML). I'm going to start my masters program in computer science and have previous experience in classical machine ...
Carlos Alfredo Vergara Rojas's user avatar
4 votes
0 answers
99 views

Active areas of research for NISQ algorithms

What areas of research in NISQ algorithms have heavy focus? I'm interested in quantum chemistry algorithms because of previous work (e.g. VQEs), and I'd love to learn more about other near-term ...
C. Kang's user avatar
  • 1,716
2 votes
2 answers
160 views

Software for Quantum Computing

From what I read classical computing evolved so quickly because of the funding-applications cycle. Even though the cost to make denser IC's was increasing rapidly, the applications were also getting ...
Jumanji's user avatar
  • 21
7 votes
1 answer
377 views

Most efficient way for general state generation

Assume we are given an $n$-qubit system and complex numbers $a_0, \ldots, a_{m-1}$ with $m = 2^n$. Assume further we start with the initial state $|0 \ldots 0\rangle$ and want to make the ...
tobias's user avatar
  • 171
5 votes
1 answer
232 views

Where does the Xmon simulator from Googles cirq framework its entropy from?

Measurements create entropy as we all know. But computers themselves are deterministic machines. Most devices use processor heat as a source for random number generation as far as I know - which has ...
sycramore's user avatar
  • 325
10 votes
1 answer
392 views

Minimum number of CNOTs for a 4-qubit increment on a planar grid

Recently I've been wondering how high NISQ machines will be able to "count". What I mean by that is, given the most optimized increment circuit you can make, how many times can you physically apply ...
Craig Gidney's user avatar
15 votes
4 answers
1k views

What use has quantum computing been?

Most of us on this site believe that quantum computing will work. However, let's play devil's advocate. Imagine that we suddenly hit some fundamental stumbling block that prevented further development ...
DaftWullie's user avatar
11 votes
1 answer
367 views

Devising "structured initial guesses" for random parametrized quantum circuits to avoid getting stuck in a flat plateau

The recent McClean et al. paper Barren plateaus in quantum neural network training landscapes shows that for a wide class of reasonable parameterized quantum circuits, the probability that the ...
Daniel Yaacov's user avatar
53 votes
2 answers
20k views

What is meant by "Noisy Intermediate-Scale Quantum" (NISQ) technology?

Preskill introduced recently this term, see for example Quantum Computing in the NISQ era and beyond (arXiv). I think the term (and the concept behind it) is of sufficient importance that it deserves ...
agaitaarino's user avatar
  • 3,827
14 votes
4 answers
1k views

How should different quantum computing devices be compared?

In the last years, there has been a spur of demonstrations of devices able to perform proof of principle, small-scale, non-fault-tolerant quantum computation (or Noisy Intermediate-Scale Quantum ...
glS's user avatar
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