Questions tagged [physical-realization]

For questions about practical computers or processors that run on a quantum architecture. This is for questions about the machines themselves, not just any computing that could take place on one. You may also use this tag for questions on realistic implementations of quantum channels. 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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28
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4answers
3k views

How do I add 1+1 using a quantum computer?

This can be seen as the software complement to How does a quantum computer do basic math at the hardware level? The question was asked by a member of the audience at the 4th network of the Spanish ...
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In D-Wave's universal quantum computer, why does the YY term have to be driven along with the linear X term?

D-Wave has a new prototype annealer that uses a Hamiltonian which, if there was enough qubits and sufficient control, would be able to simulate any universal circuit-based quantum computer with at ...
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2answers
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How does a quantum computer do basic math at the hardware level?

On reading this Reddit thread I realized that even after a couple months of learning about quantum computing I've absolutely no clue about how a quantum computer actually works. To make the question ...
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Is Google's 72 qubit device better than D-Wave's machines, which feature more than 2000 qubits? [duplicate]

Google recently announced the Bristlecone 72 qubit quantum computer. However, D-Wave already announced quantum computers featuring more than $2000$ qubits. Why is Google's new device newsworthy then? ...
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478 views

How to explain in layman’s terms the significance of the difference of qubits of the D-Wave and IBM QX?

So, @AndrewO mentioned recently that he has had 'encounters' with people wondering why D-Wave has a lot more qubits than IBM. Of course, this comparison is faulty, since the IBM and D-Wave's machine ...
19
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3answers
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Why do optical quantum computers not have to be kept near absolute zero while superconducting quantum computers do?

This is a follow-up question to @heather's answer to the question : Why must quantum computers be kept near absolute zero? What I know: Superconducting quantum computing: It is an implementation of ...
22
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3answers
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What is the argument that practical quantum computers cannot be built?

An answer to another question mentions that There are arguments that suggests that such machines ["quantum Turing machines"] cannot even be built... I'm not sure I fully understand the problem,...
13
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2answers
681 views

Why must quantum computers be kept near absolute zero?

Online descriptions of quantum computers often discuss how they must be kept near absolute zero $\left(0~\mathrm{K}~\text{or}~-273.15~{\left. {}^{\circ}\mathrm{C} \right.}\right)$. Questions: Why ...
12
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1answer
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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 ...
19
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1answer
466 views

What cryogenic systems are suitable for superconducting qubits?

Is a dilution refrigerator the only way to cool superconducting qubits down to 10 millikelvin? If not, what other methods are there, and why is dilution refrigeration the primary method?
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630 views

Is the “Quantum Volume” a fair metric for future, elaborate, high value quantum computations?

A metric called the "quantum volume" has been proposed to somehow compare the utility of different quantum computing hardware. Roughly speaking, it measures their worth by the square of the maximum ...
10
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How power-efficient are quantum computers?

As we all know, 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 ...
9
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What is D-Wave's “Pegasus” architecture?

How is D-Wave's Pegasus architecture different from the Chimera architecture?
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1answer
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Do we really know how a universal quantum computer can be used to revolutionize the design of new drugs or materials?

One of the most promising applications of a quantum computing is the design of new drugs and materials: Quantum computers promise to run calculations far beyond the reach of any conventional ...
11
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How are quantum gates realised, in terms of the dynamic?

When expressing computations in terms of a quantum circuit, one makes use of gates, that is, (typically) unitary evolutions. In some sense, these are rather mysterious objects, in that they perform "...
10
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1answer
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Does the D-Wave 2000Q satisfy DiVincenzo's criteria?

DiVincenzo's criteria for quantum computation are the following: A scalable physical system with well characterized qubits. The ability to initialize the state of the qubits to a simple fiducial ...
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Allowed CNOT gates for IBM Q 5 quantum computer

I trying to do some tests in the IBM Q5 computer of IBM quantm experience for some simple error correction protocols, but as I can see, some operations between the qubits are not allowed. For example,...
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Processing density capabilities in a quantum processor

Given the theoretical infinite quantum states that a qbit can be expressed as is there any practical limit to the processing density in any given quantum processor as compared to the absolute limits ...
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Scale for Quantum Computing [closed]

Does something like Mohs' scale exist for quantum computing? (eg. classical = 0, hybrid = 5, pure quantum = 10) Mohs' scale: a scale of hardness used in classifying minerals. It runs from 1 to 10 ...