Questions tagged [models]

For questions on theoretical models of quantum computations. Such models may be realistically 'build' in real machines, but not necessarily.

Filter by
Sorted by
Tagged with
7 votes
1 answer
122 views

Are ladder operators ever extensively used in any model of quantum computation?

Computer scientists and others who are interested in learning more about quantum computation might be exposed, or re-exposed, to various concepts and classes of matrices from linear algebra. For ...
user avatar
  • 7,017
3 votes
1 answer
30 views

Why does the condition $\langle \varphi _k\left( t \right) |\dot{\varphi}_l\left( t \right) \rangle =0$ called parallel transport condition?

I'm reading this paper about nonadiabatic holonomic quantum computation and met the condition eq.(2) states that $\langle \varphi _k\left( t \right) |\dot{\varphi}_l\left( t \right) \rangle =0$ is the ...
user avatar
  • 515
1 vote
0 answers
37 views

How to simulate $H(\theta) = B(\sin\theta S_1^x +\cos\theta S_1^z +\sin\theta S_2^x +\cos\theta S_2^z)+aS_2^zI_z$ on IBM Qiskit

I am trying to simulate this Hamiltonian on IBM Qiskit, for varying values of $\theta$: $H(\theta) = B(\sin\theta S_1^x +\cos\theta S_1^z +\sin\theta S_2^x +\cos\theta S_2^z)+aS_2^zI_z$ Where S is ...
user avatar
1 vote
0 answers
21 views

What is the relation between the database made up of N elements and the index made up of a string length n in the query model?

I am working on a circuit model that contains a blackbox (query) and do not understand the relationship between what is in the black box and the way we get out the value of the element we index. The ...
user avatar
0 votes
1 answer
123 views

unexpected effect of coherent unitary error in qiskit

I'm trying to simulate the effect of a coherent unitary Z rotation at an arbitrary angle of a single qubit on the fidelity of a quantum circuit. I am using the qiskit Aer noisy simulator. More ...
user avatar
  • 998
3 votes
0 answers
50 views

What type of tasks it is possible to solve on a quantum simulator?

In this article, the author claimed that researches from Harvard and MIT created 256 qubits quantum simulator. However, we are not talking about piece of software on a classical computer but actual ...
user avatar
5 votes
1 answer
109 views

Where is entanglement present and absent in the one clean qubit model of computation?

Based on my limited and poor understanding, a quantum circuit in the "one clean qubit" model of quantum computation generally acts on a single pure (clean) qubit tensored with $n-1$ qubits ...
user avatar
  • 7,017
3 votes
0 answers
52 views

Modeling building blocks for quantum computation

If I would design library for quantum computation I would naively consider a sequences of entangled qudits with unit length as a building blocks. I.e., unit length elements from $$\mathbb{C}^{d_{1}}\...
user avatar
2 votes
1 answer
104 views

What does "large-scale universal quantum computation" mean?

I was reading this lecture notes by Sevag Gharibian. He mentioned the following statement: Large-scale universal quantum computer can be built. I do understand what quantum computer is, but I don't ...
user avatar
  • 255
3 votes
1 answer
165 views

Applications of Quantum Computing to Economics

I have recently been interested in the field of 'Econophysics' which as I understand it is the practice of basically applying results of physics in areas such as non-linear dynamics and stochastic ...
user avatar
1 vote
1 answer
84 views

PreciseQMA = PreciseBQP gives PP = PSPACE

$\text{PreciseBQP}$ is defined as $\text{BQP}$ with inverse exponentially close completeness and soundness bounds (for a better definition, see Section 3.1 here, in the paper by Gharibian et al). ...
user avatar
4 votes
1 answer
327 views

Proof that any unitary can be written as $U=e^{-iH}$ with $H$ Hamiltonian with bounded norm

I am looking for a proof that any unitary matrix can be written as: $$U = e^{-iH}$$ where $H$ is some Hamiltonian with bounded norm. That is $$||H||_{2} = O(1).$$
user avatar
1 vote
1 answer
76 views

IBM Q Experience - Can it be used draw out ML inferences? [closed]

Are there Quantum-enhanced Machine Learning algorithms that can be implemented via Qiskit in IBM Q Experience and obtain valuable inferences faster than their classical counterparts from datasets of ...
user avatar
  • 23
1 vote
0 answers
53 views

Screening procedure in an iterative qubit coupled cluster (iQCC) ansatz

The paper Iterative Qubit Coupled Cluster approach with efficient screening of generators describes a new screening procedure for generators of the QCC ansatz. How does one get from defining the ...
user avatar
  • 111
1 vote
0 answers
41 views

Can We Currently Import Quantum Datasets (Datasets Containing Quantum Data) Onto NISQ-era Quantum Computers?

I'm still investigating the TFQ whitepaper. In one section of the paper, the authors say this with respect to Quantum Datasets In general, [a quantum dataset] might come from a given black-box ...
user avatar
1 vote
0 answers
48 views

Application Query [closed]

I had written earlier to propose an econometric modeling application that may lend itself to a quantum computing approach, and was asking how best to proceed. The model would be centered around the ...
user avatar
  • 11
2 votes
1 answer
542 views

How to measure one of the qubits in a two-qubit register?

How do I measure the first qubit of an entangled vector, say \begin{pmatrix} 1 \\ -1 \\ 0 \\ 0 \\ \end{pmatrix} is what I get on the end of Deutsch's algorithm. If I get it right, I should now ...
user avatar
0 votes
0 answers
85 views

How close are we in achieving computation over reals using quantum qubits? [duplicate]

I recently attended a seminar where a professor of quantum cryptography told the audience that one quantum qubit can theoretically store "infinite information". I was very intrigued by this statement, ...
user avatar
3 votes
2 answers
334 views

Is quantum parallel search impossible?

Scott Aaronson's blog notably states: Quantum computers would not solve hard search problems instantaneously by simply trying all the possible solutions at once. Is this a statement of a law, as ...
user avatar
  • 1,240
4 votes
1 answer
108 views

Why do quantum computation models based on open quantum systems receive so little attention?

In almost all research on (universal) quantum computation the common models assumed from the outset are either the quantum circuit model with unitary gates, the measurement-based one-way model or the ...
user avatar
3 votes
0 answers
112 views

Why is the resource theory approach used in quantum information processing? [closed]

What are the advantages and applications of using the resource theory approach in QIP ? What specific problems can be solved using in particular this approach ?
user avatar
1 vote
1 answer
63 views

Is there an inherent difference in need for error correction between quantum annealing and gate based methods?

When I read about computing using gate based methods, I mainly read about the difficulties with error rates, circuit depth (and connectivity) and not enough qubits. With computing using quantum ...
user avatar
3 votes
1 answer
128 views

Aren't reversible logic gates a necessity for efficiently executing quantum algorithms?

The Wikipedia article on logical reversibility says: ...reversible logic gates offered practical improvements of bit-manipulation transforms in cryptography and computer graphics. But I guess ...
user avatar
7 votes
0 answers
78 views

Correspondence between the Topological model and Quantum Circuit model

For example, given the $R$ & $F$ gates and Toric codes for a given problem, how to convert this code into the conventional circuit model and vice versa. From the literature developed, it seems ...
user avatar
4 votes
2 answers
172 views

Quantum computing concepts

I am trying to develop a feel for quantum computing at a basic level. I would very much appreciate someone will take a look at the statement below and fix it, since I assume it needs fixing. “...
user avatar
8 votes
1 answer
162 views

What good references would you recommend to understand the (continuous-variable) CV model of computation?

If you have good references about the CV model that are understandable from a computer science background, that would be great. If they include numerical examples, that would even be better.
user avatar
  • 4,564
5 votes
1 answer
166 views

What is continuous quantum register and how it relates to qubits?

I would like to understand what is a continuous quantum register. I know the direct definition is a quantum register that stores a real number defined by an observable with a spectrum consisting of $\...
user avatar
  • 4,564
6 votes
2 answers
774 views

What exactly are "quantum rotors"?

The Wikipedia entry on the subject is rather short. I am also curious about generalizations of quantum rotors in n-dimensions. An introductory explanation with at least one resource for further ...
user avatar
  • 3,202
10 votes
3 answers
710 views

What is the simplest algorithm to demonstrate intuitively quantum speed-up?

What's the simplest algorithm (like Deutsch's algorithm and Grover's Algorithm) for intuitively demonstrating quantum speed-up? And can this algorithm be explained intuitively? Ideally this would be ...
user avatar
7 votes
2 answers
2k views

What are the pros/cons of Trapped Ion Qubits, Superconducting Qubits and Si Spin Qubits?

Among available qubit technologies for universal quantum computing these 3 come up as promising. NV centers and Majorana qubits also underway but relatively new. I find superconducting qubits and ...
user avatar
  • 355
6 votes
2 answers
217 views

Anyon alternatives in topological quantum computing

A topological quantum computer is a theoretical quantum computer that employs two-dimensional quasiparticles called anyons. -Wikipedia Are there other instances of topological quantum computing ...
user avatar
  • 3,202
4 votes
1 answer
281 views

Chrononic Computing (Time Evolution Systems)

In a recent question about quantum speed-up @DaftWullie says: My research, for example, is very much about "how do we design Hamiltonians $H$ so that their time evolution $e^{-iHt_0}$ creates ...
user avatar
  • 3,202
9 votes
1 answer
176 views

Where can I find example circuits to learn from?

I'm relatively new to quantum computing and my goal is to learn how to implement algorithms that I read in papers. While I have found many circuit snippets I have yet to find a repository of examples ...
user avatar
5 votes
3 answers
1k views

Is it possible to simulate a quantum computer in Virtual Reality? If yes, how?

There have been a couple of simulations already made and I recently saw this high performance, hardware accelerated quantum computer simulator QCGPU and started to wonder about how to simulate quantum ...
user avatar
8 votes
1 answer
1k views

What are the fundamental differences between trapped ion quantum computers and other architectures?

There are many different ways to build quantum computers, such as superconducting qubits, quantum dots, and ion traps. What I would like to understand is why some universities and research ...
user avatar
  • 203
23 votes
2 answers
3k views

What is the difference between quantum annealing and adiabatic quantum computation models?

From what I understood, there seems to be a difference between quantum annealing and adiabatic quantum computation models but the only thing I found on this subject implies some strange results (see ...
user avatar
  • 4,477
13 votes
0 answers
215 views

Does the Curry-Howard correspondence have a quantum-specific type system?

In Wikipedia we can read that the Curry–Howard correspondence is a correspondence between formal proof calculi and type systems for models of computation. In particular, it splits into two ...
user avatar
  • 744
17 votes
2 answers
638 views

In a Quantum Turing Machine, how is the decision to move along the memory tape made?

Let, for a Quantum Turing machine (QTM), the state set be $Q$, and the alphabet of symbols be $\sum=\{0,1\}$, which appear at the tape head. Then, as per my understanding, at any given time while the ...
user avatar
19 votes
2 answers
1k views

How does topological quantum computing differ from other models of quantum computing?

I've heard the term Topological Quantum Computer a few times now and know that it is equivalent to quantum computers using circuits with respect to some polynomial-time reduction. However, it is ...
user avatar
  • 492
5 votes
1 answer
112 views

Which theoretical models for quantum computing are polynomial-time equivalent? [duplicate]

There are different theoretical models for quantum computing like the circuit model or the model of adiabatic quantum computers. Between which of these models exist polynomial-time reductions? Note ...
user avatar
  • 492
12 votes
3 answers
476 views

Who built the first quantum computer using at least two qubits?

In my previous question I asked who invented a quantum computer using qubits. As a follow-up to this question I want to ask who built the first quantum computer using at least two qubits. During my ...
user avatar
  • 1,027
24 votes
2 answers
2k views

Why can't quantum annealing be described by a gate model?

This is a question I was inspired to ask based on this question, which notes that quantum annealing is an entirely different model for computation than the usual circuit model. I've heard this before, ...
user avatar
57 votes
6 answers
4k views

What are the models of quantum computation?

It seems that quantum computing is often taken to mean the quantum circuit method of computation, where a register of qubits is acted on by a circuit of quantum gates and measured at the output (and ...
user avatar
  • 1,815