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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References discussing the carbon footprint expected for fault-tolerant quantum computers?

There are many problems regarding the scalability of quantum computers, how we need good quantum error correcting codes that scale well and protect well the logical encodings against many possible ...
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Using entropy quantum computing for solving optimization problems

I would like to follow up on this question (What is Entropy Quantum Computing?). Company Quantum Computing Inc. announced that they made their quantum computer aimed at solving binary optimization ...
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Difference between IBM and Google Quantum Circuit?

I am wondering what the internal differences between IBM and Google quantum circuits are. They look so different. Google team seems to design their circuit in a fully-connected manner, while the chips ...
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What is Entropy Quantum Computing?

Recently there is news concerning some computational breakthroughs by using so-called "entropy quantum computing": https://thequantuminsider.com/2022/07/20/qci-solves-3854-variable-problem-...
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Why can two atoms can be entangled?

As a qubit is a two-state (or two-level) quantum-mechanical system, one of the simplest quantum systems displaying the peculiarity of quantum mechanics. Examples include the spin of the electron in ...
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Can the paper by Monz et al. (2015) be regarded as a real implementation of Shor's algorithm?

I'm studying about the Shor algorithm and I wonder whether the paper below can be regarded as a real implementation of the Shor algorithm: https://arxiv.org/abs/1507.08852 In this paper, they tried to ...
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The world's first quantum integrated circuit at the atomic scale - How does this advance quantum computing as a whole?

I have a hobbyist/enthusiast understanding of Quantum Computing, having read a few books on the subject. I came across this new article and referenced Nature paper. I know a goal of quantum computing ...
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Are there hardware platforms that natively implement parametric two qubit gates?

For example, is it possible to implement RXX gate with an arbitrary angle on an ion computer in a single native operation? The RXX gate with an arbitrary angle can be decomposed into two RXX gates ...
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How are IBM's 127 qubits more potent than the 5760 qubits D-Wave - Advantage_system6.1?

Hi I'm a newbie in quantum computing recently I had a look at the AWS braket and I've seen they had a machine called D-Wave - Advantage_system6.1 that has 5760 qubits but when I googled the highest ...
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Is there the number of CNOT restriction?

I know that there is connectivity restriction when implementing physical CNOT gate. But, I wonder if there is a limit to the number of physical CNOT gates that can be performed at the same time. For ...
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The energy levels crossover problem in Quantum Annealing

How to avoid energy levels crossover in quantum annealing by Kibble-Zurek mechanism? Any detailed references?
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Does "detecting and characterizing quantum information [electron spin quantum states]" satisfy statement 5 of DiVincenzo's criteria?

I am reading a company's (Archer Materials) press release on their progress towards building a quantum computing chip and I have a question about how a certain statements are phrased: Archer’s 12CQ ...
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Is there a toy oracle to show the feasibility of Grover's algorithm?

Is there any small 'toy' oracle that can show the feasibility of Grover's algorithm for searching (without using the geometric rotation interpretation)? It is confusing that we cannot know the ...
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Do quantum states with a single parameter give any theoretical or experimental advantage compared to multi-parameter ones?

If a quantum state is a single parameter two-qubit mixed entangled state then is there any theoretical or experimental advantage compared to a multi-parameter state? suppose, we take a single ...
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Experience on analog chaos based qc?

Any expirience on applied analog qc using a chaos based approach. By chaos I mean using analog components in chaos state thus changing between a wide range of states simultanously. The initial work on ...
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What physically limits qubit connectivity in superconducting chips?

All the superconducting based quantum computers I'm familiar with have a maximum of 4 nearest neighbors per qubit. Trapped ion architectures seem to be able to drive entangling gates between all pairs ...
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What is the quantum leap / advantage of quantum computers? [duplicate]

I have read up several times on various sources about the advantage of quantum computers but still, I can only reproduce statements without really understanding them. Why are quantum computers able to ...
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Individual processing of quantum circuit measurment results

When superconducting transmon qubits are measured with a readout pulse, the raw readout signal is demodulated, and results appear as clouds on the IQ plane, with one point in the cloud representing ...
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Why does making a quantum circuit more noise resilient make it easier to simulate classically?

I was reading Quantum Computing in the NISQ era and beyond (John Preskill, 2018) but I didn't get this point on pages 9-10: There is a substantial opportunity for experimentalists and theorists, ...
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How do we know that a superconducting circuit is a quantum system?

In introductions to superconducting qubits, we often take the classical LC circuit and then quantize the operators. Why are we allowed to do this? I do not see this derivation anywhere -- what ...
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How are gates implemented in a transmon qubit?

A transmon qubit is fundamentally in LC circuit. How are gates implemented in a transmon qubit? How do we know what voltage corresponds to the $\sigma_x$ gate for example?
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In a transmon qubit, what corresponds to the ground and excited states?

In a transmon qubit, we have ground and energy eigenstates but what is actually happening in the circuit here? How do the current and voltage look? It looks like its made up of things you would find ...
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What are the typical gate times for single-qubit and 2-qubit gates for ion trap, superconducting, neutral atom, photonic, spin QC?

What are the typical gate times for single-qubit and 2-qubit gates for -- ion trap, -- superconducting, -- neutral atom, -- photonic, -- spin quantum computers based on today's technologies?
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How many physical qubits are needed to encode a logical qubit on ion trap, superconducting, neutral atom, photonic QC?

How many physical qubits are needed to encode a logical qubit on an -- ion trap, -- superconducting, -- neutral atom, -- photonic, -- spin quantum computer based on today's technologies?
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What are useful abstraction levels for external quantum input/output of quantum computers?

Section "2.2.3 Quantum measurement" in Nielsen&Chuang uses very general measurement axioms: Postulate 3: Quantum measurements are described by a collection $\{M_m\}$ of measurement ...
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How to implement gate which is like Identity but multiplied on "i"

In my program I need a single qubit processing gate which implements logic like this: |0> ==> i*|0> |1> ==> i*|1> This is like Identity gate but multiplied on "i" I ...
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What are introductory resources to learn about quantum computing hardware?

I am interested in learning some details of quantum computers inner working, what are the limitation etc. in order to understand quantum computation more. Can some one refer me to some good materials ...
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Quantum communications and "knowledge" of receiving a qubit

Question from a computer scientist (not a physicist). Imagine two nodes on a quantum network. Alice sends Bob a qubit in some state of superposition over a quantum channel. Is Bob able to sense that ...
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What does it mean for a channel to be independent of the input state?

A 2007 paper shows how to construct quantum channels on finite-dimensional Hilbert spaces $$\sigma=\Phi(\rho)=\sum_i K_i \rho K_i^\dagger,\qquad \sum_i K_i^\dagger K_i=\mathbb{I}$$ for which $\Phi(\...
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Do individual qubits on IBM quantum processors share the same control unit?

I want to investigate the maximum possible parallelism of quantum operations on a specific IBM device (such as the latest heavy-hex architecture), which requires a basic knowledge of their control ...
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How to obtain control and drift Hamiltonians for device in Qiskit?

I would like to play around with Qiskit OpenPulse and the publicly available IBMQ quantum computer that supports OpenPulse. My humble goal is to use Qutip's optimal control libraries to get a pulse ...
4 votes
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How to formulate Dynamical Decoupling passes in Qiskit to improve result upon circuit execution

First, let me say that I am not familiar with the idea of Dynamical Decoupling. The goal of this question is to understand how to set up a circuit with dynamical decoupling to improve my hardware ...
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How can time crystals be useful in qRAM design?

A time crystal is a phase of a matter which is ordered in time, similar to classical crystals which are ordered spatially. In other words, the structure of a time crystal is ever-changing but with ...
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What is the justification for the use of this arbitrary post-processing vector?

I am reading through this paper which describes the use of a post-processing vector $\vec{c}$ with elements having values of $(-1,0,1)$. In equation 3 they give their solution as a linear combination ...
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Does QRNG generates True Random numbers?

I read an article that claims, QRNG can produce a true random number. So I wonder, how could they prove that this is a true random numbers generator? In fact, imagine I look at my memory state and ...
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Why do we have to measure the circuit before sending it to the real quantum computer?

If I want to run a circuit on a real quantum computer, I have to measure it before running it. For example: ...
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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 ...
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What does a quantum logic gate look like in a universal quantum computer?

I am familiar with logic gates which are in classical computers. They are made up of semiconductor devices like diodes and transistors. There are some companies which are working on the universal ...
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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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What are the most popular QND measurement implementations used in photonic quantum computers?

What components are used in order to perform QND measurement in photonic quantum computers?
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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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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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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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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 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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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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