Questions tagged [physical-realization]

For questions about physical implementations of a quantum algorithm or other quantum information protocol. DO NOT use for questions about simulation or emulation of quantum computers, or cloud-based quantum computing services like the IBM Q Experience.

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What is an electro-optic switch?

I found an implementation of a CNOT in photonic QC and I just couldn't find any info on a component named "electro-optic switch" What does it do exactly? How does it work? The ...
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Why is entanglement creation difficult?

No matter from the true physical realization to date or from some papers, it seems that multipartite entanglement creation is difficult. However, the circuit showing below can easily create ...
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How does the CNOT gate operate when the control qubit is a superposition?

If a control qubit is in superposition, how it will affect target qubit if it is collapsed or in superposition? Is it true that CNOT works only if the control bit collapsed to 1? Also, is it possible ...
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How does measuring in the $|\pm\rangle$ basis works in experiments?

I don't get how measuring in different bases works in experiments. From an experimental point of view, what do we do to measure in $|\pm \rangle$ basis? If I'm getting it right measuring in the ...
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How do quantum computers implement a random unitary gate?

If I from qiskit.quantum_info import random_unitary and then random_unitary(2**number_of_qubits) What returns is a unitary ...
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Is this QEC scheme technology dependant? [closed]

Is this [1] type of error correction also usable for ion-trap based quantum computers? Is it quantum technology dependent? [1] P. Das et al., “A Scalable Decoder Micro-architecture for Fault-Tolerant ...
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Does a quantum computer exist today? [closed]

I agree that this may not be an easy question to answer. But lately, I increasingly come across the fact that many news materials and research papers in the field of quantum technologies say that at ...
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Quantum computer speedups for classically efficient applications

I'm interested in learning about cases where a quantum computer could be used to perform tasks with only a constant (albeit large) factor of improvement in execution speed over classical computers. ...
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Is it possible to perform quantum computation between different Hilbert spaces?

Let us consider a protocol between Alice and Bob. Alice works in a $2^n$-dimensional Hilbert space $\mathcal{H}_A$, using $n$ qubits. Bob works in a $(1+2^n)$-dimensional Hilbert space using qdits. ...
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Why attenuator and not filters for QC driving line

In all the cold quantum computer designs (superconducting qubits, spin qubits) attenuators are put on the driving lines. Their role is to kill the noise spectral density that comes from higher ...
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Counting channel uses of the lossy bosonic channel or definition of channel uses

The PLOB-bound ("Fundamental Limits of Repeaterless Quantum Communications") gives an asymptotic upper bound on the secret-key rate per used lossy bosonic channel. However, I'm not sure how to count ...
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Software used for modelling quantum processors

What kind of software is used for modelling quantum processor architectures? Not just simulate the output, but the one that is actually used in research.
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Is it possible to design a Quantum Computing Advantage to deploy an application on the web?

I need to understand the frontier and practical applications of quantum computing. Is it possible to design a Quantum Computing Advantage to deploy an application on the web, such as a browser, ...
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Claimed “potential revenue” from machine learning in 2023?

In this plot: taken from here, IonQ is claiming to have a potential application in machine learning by 2023. What applications could they have in mind? From what I understand, modern error correction ...
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Is there any quantum gate that can change quantum hardware topology(architecture)?

I read about this paper Hardware-aware Heuristic for the Qubit Mapping problem in the NISQ Era. I wonder there is the only SWAP gate that can change the quantum hardware topology. Is there any gates ...
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How are witness operators physically implemented?

Let's take an example of an entanglement witness of the form $W = | \phi \rangle \langle \phi | ^{T_2}$ where $ | \phi \rangle $ is some pure entangled state. If I wanted to test some state $\rho$, I ...
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Are classical analogues of quantum computers using superposed waves possible? [duplicate]

The trick of quantum computing is to take the advantage of wave mechanics (superposition) and entanglement. This allows to perform parallel computations/manipulations with $2^n$ superposed waves for $...
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Crosstalk error of simultaneous cnots

We can use simultaneous randomized benchmarking (SRB) to quantify the crosstalk impact of simultaneous CNOTs. The crosstalk error is caused by many reasons, for example, the always-on ZZ interaction, ...
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How significant is achieving electronic transport in a single qubit at room temperature?

This is a follow-up to a previous question I asked: How promising is the possibility of carbon-based qubits to make a qubit that’s stable at room temperature? I am trying to assess the significance of ...
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How are quantum gates implemented in reality?

Quantum gates seem to be like black boxes. Although we know what kind of operation they will perform, we don't know if it's actually possible to implement in reality (or, do we?). In classical ...
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How is the Grover iteration realized in an actual quantum circuit?

The number of the Grover's diffuser iterations is proportional to square root of the amount of input data, but how is this realized when building a real quantum circuit? Is it simply by concatenating ...
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How power-efficient are quantum computers?

Quantum algorithms scale faster than classical ones (at least for certain problem clases), meaning quantum computers would require a much smaller number of logical operations for inputs above a given ...
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How to do the counting when computing the fault tolerant threshold of quantum codes?

Here, I want to ask a basic question about how to compute the fault tolerance threshold of quantum codes. As I know, maybe, the most usual way is to do some simulations. Howvever, I am more intersted ...
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Where does the energy go in a Power Rabi experiment with superconducting circuits?

When performing a Power-Rabi experiment, e.g in superconducting circuits, we are playing a pulse to a qubit and then reading out its state by playing another pulse to a dispersively-coupled readout ...
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Is it possible to have access to real quantum computers that have more than 15 qubits for my master thesis?

My physics master thesis is about variational quantum optimization and I have to run algorithms with more qubits than 15. Is it possible to make any requests to use larger IBM real quantum computers?
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Up to date overview of experimental approaches to quantum computing

I'm interested in getting an overview of the leading approaches to quantum computing from a physics perspective. I've read most of Nielsen and Chuang, but its chapter on physical realizations looks ...
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What are Sideband Pulses

I see sideband pulses used all over the place when looking up implementation techniques especially in Trapped Ion QC. Is there a layman's explanation of what they actually are? I understand what they ...
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Topology graphs of IBM's quantum computers

What is the meaning of the topology graphs of IBM's quantum computers? How should it be interpreted? For example, how should I understand the following graph?
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Does this experimental discovery of anyons enables the topological quantum computer (e.g. Microsoft) to become a reality?

Microsoft has its own agenda regarding quantum computer - it is topological quantum computer being invented by the team lead by Michael Freedman https://www.microsoft.com/en-us/research/project/...
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Are there any detailed designs for Quantum Computing hardware?

I am looking to analyze some quantum hardware designs, preferably superconducting and photonics, but I can't seem to find sources that give some detailed information. Can someone provide me designs ...
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Is there a quantum processor with physically implemented Toffoli gate?

Recently, I came across the article Realization of efficient quantum gates with a superconducting qubit-qutrit circuit where its authors proposed a physical implementation of three qubits quantum ...
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How do we realise photonic gates?

I am interested in photonic computing, and I am curious how the gates work. I once saw a picture of a photonic CNOT gate that used just mirrors and polarizers. I have not been able to find any ...
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Is Grovers Algorithm Oracle creation a hardware level aspect?

There are numerous questions that asks about practical application demonstration of the Grover algorithm for arrays and databases. However examples are not seen anywhere. While searching for its ...
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Can the (universal) state inversion operator be physically realized?

I was trying to solve an exercise from Vazirani's course "Qubits, Quantum Mechanics and Computers": A mathematically nice, but unphysical, way to detect entanglement is to use the state ...
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How are the IBM's and Google's Hadamard gates fabricated and operated?

There are thousands of articles, books and web sites describing the Hadamard Gate from a theoretical point of view. But I haven't been able to find any photo about any real implementeation of a ...
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Gate characteristics of different platforms

I would like to know if there is a place in which is summarized the gate characteristics of the different quantum computer existing (IBM,Google, others). For instance, which kind of two qubit gate ...
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Which subatomic particle does each company use in quantum computing?

Probably each company (Google, Amazon, Intel, IBM, Microsoft, D-Wave and so on) uses a mix of subatomic particles and technologies. I would like to know which particles/technologies are used by each ...
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Average execution time for T gate

Using the Q# resource estimator, I found out that my program, meant to do graph coloring using Grover's algorithm, could be decomposed into ~500-1000*x T gates, where x in the number of iterations, ...
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How can I achieve single-qubit $T$ operation using spin resonance?

We know that $T$ gate is as follows $T=\left(\begin{array}{cc}1 & 0 \\ 0 & e^{i \pi / 4}\end{array}\right)$ And on the other resultant spin-resonance hamiltonian is $\frac{H}{\hbar}=\frac{1}{2}...
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Is there a straightforward way to calculate the quantum volume for simple systems?

There are a few people who ask how to calculate IBM's "quantum volume", but it's not clear what the actual mathematical definition of this is. In the answers here, people just point to ...
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Physical implementation of gates on IBM Q

There is a lot of quantum gates in IBM Q Composer, however, only few are implemented physically while others can be composed of them. When one looks at description of a quantum processor in IBM Q ...
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Are we certain that quantum computers are more efficient than classical computers can be built?

I mean are we certain that they will be able to provide us a huge improvements (in some tasks) compared to clasical computers?
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Which type of quantum computer is explained by spin-boson Hamiltonian?

In a review paper of decoherence-free subspace(DFS) [1], they consider the spin-boson Hamiltonian and they write the system of qubits could be the spins of N electrons trapped in the periodic ...
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Why is it harder to build quantum computers than classical computers?

Is it because we don't know exactly how to create quantum computers (and how they must work), or do we know how to create it in theory, but don't have the tools to actually execute it in practice? Is ...
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Why isn't NV-center-based quantum computing mainstream?

One can rattle off names of implementations of Superconducting Qubits, transmon qubits, etc For example, see Physical realizations used by Google But NV centre Qubits as in this question, Is there any ...
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Is there any company trying out ion trap qubits?

Analogous to this question Is there any company that backs and implements diamond vacancy quantum computers?
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quantum circuit with feasible gates for state preparation

I have a classical vector of size $2^{n}$ (normalized) and I want to use this value as amplitude for my $n$ qbits, in the canonical basis $|00000\rangle$, $|00001\rangle$ etc. I want to use real ...
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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 (...
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Exponential Growth of Noise in Quantum Computers

I recently listened to a presentation for Introductory Quantum Computing. It was very general and meant to give the listeners an idea about the potential for Quantum Computing. The speaker ended the ...