Questions tagged [architecture]

For questions related to building of quantum computers and discussion of the hardware aspects.

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Physical qubit of optical quantum computer

I was researching how optical quantum computers work and discovered a KLM protocol that allows for building quantum gates using linear optics elements like mirrors, beam splitters, and phase shifters. ...
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IBM Q devices' hardware/resource constraints

I tried to look for the resource constraints but so far haven't been able to find them. They are not present in the GitHub repository that usually provides the hardware information for the different ...
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How is a physical qubit measured and how is the result interpreted?

To my understanding, most of the qubits we use today are just Josephson junctions coupled to a resonator that is triggering the qubits to go to different states by using microwave pulses. The same ...
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Current limits on Grover search space

I was wondering why till date Grover search has been implemented only till 3 qubits (corresponding to size of database = 8). Refer this paper The reason why I ask is that we have much larger sized ...
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Spin precession using a laser

According to Christopher Monroe: "Modular Ion Trap Quantum Networks: Going Big", the hyperfine states of the valence electron in the Yb+ is used as a qubit. I know that we can change the spin ...
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What is the “TRIAD” graph and where can I find more information about it?

I was looking up how to program for a D-Wave machine and I came across this image which says it's the "optimal hardware graph" for a D-Wave machine: Unfortunately the image seems to have come from ...
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Understanding (theoretical) computing power of quantum computers

I am very new to quantum computing and just try to understand things from a computer scientist's perspective. In terms of computational power, what I have understood, 100 ideal qubits ... can ...
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When and where was the first use of the term Chimera?

This is along the same lines as the earlier question: When was the first use of the word Entanglement? I was surprised to discover that when searching for "chimera" in both of Vicky Choi's minor-...
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Can quantum computers be clustered together?

I have been interested in the idea of computer clusting which is about making multiple pysical computer system to act as one whole logical computer system computing the same task at the same time, but ...
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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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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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Can a stored programming model be applied to a Quantum Computer?

A stored programming computer model is that where a central memory is used to store both instructions and data that they operate on. Basically all the classical computers of today that follow the von ...
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Are qubits the only elements required to build a quantum computer?

The power of a quantum computer is often described in terms of how many qubits it has. Does that mean that quantum computers can be run using only qubits, and nothing more? Wouldn't we require some ...
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Randomness from deterministic machine

It is known that in a classical computer we can't generate a purely random number by deterministic process. I am taking a course in Quantum Computing, recently I learnt that using state we can ...
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Transmons and cooper pair box qubits: two islands or a single island and a reservoir

In scientific literature, one typically describes Cooper pair boxes as a small superconducting island coupled to a superconducting reservoir (say, a large ground plane of superconducting metal, or a ...
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State of the art gate speeds and decoherence times

I am interested in the state of the art gate speeds and decoherence times for the qubit types I know are being pursued by companies presently: superconducting qubits, ion trap qubits, photonic qubits....
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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 ...
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Is it possible to purchase quantum computing hardware? [closed]

Are there schematics and/or diagrams out there to build a very basic quantum system?
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Is it possible to make our own quantum computer? If yes, what will it take? [closed]

I am thinking as quantum computing is just a new word in tech, so let to explore it by building it or a prototype based on it so I am just wanted help in setting up and initial steps which should I ...
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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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How could a quantum network be constructed to handle 10,000 clients concurrently?

The C10k Problem is a classical computing problem whose name (C10k) is a numeronym for concurrently handling ten thousand connections. How could a quantum network be constructed to handle 10,000 ...
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Why did D-Wave choose the Chimera graph the way they did?

D-Wave makes use of a $(n,k=4)$-Chimera structured graph in their computers. Meaning a $n\times n$ grid of unit cells, with each unit cell consisting of a complete bipartite graph on $2k=8$ nodes ($4$ ...
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How does the size of a toric code torus affect its ability to protect qubits?

The Toric code Hamiltonian is: $\sum_{x,y}\left( \prod_{i\in p(x,y)} Z_{ixy} + \prod_{i\in v(x,y)} X_{ixy} \right),$ where the $v$ and $p$ are defined according to this picture (courtesy of James ...
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How would a Quantum Computer (network) perform loophole-free Bell tests?

In a simple form, Bell's theorem states that: No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics. Bell developed a series of inequalities ...
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Are there any estimates on how complexity of quantum engineering scales with size?

It seems to me that an extremely relevant question for the prospects of quantum computing would be how the engineering complexity of quantum systems scales with size. Meaning, it's easier to build $n$ ...
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Translation of color/toric code to a small network of solid-state spins

Within Quantum Error Correction and stabilizer codes, toric codes/surface codes are very tempting, mainly for their high error threshold. For more background please check up, in our Physics sister (...
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Active improving of nanodiamond surfaces for NV centers?

This question is related (and complementary) to "Passive improving of nanodiamond surfaces for NV centers?". Nitrogen-Vacancy centers (NVs) have astonishing quantum properties, which make them ...
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Passive improving of nanodiamond surfaces for NV centers?

Nitrogen-Vacancy centers (NVs) have astonishing quantum properties, which make them interesting as potential hardware both for quantum computing in particular and for quantum technologies in general. ...
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Quantum simulation of environment-assisted quantum walks in photosynthetic energy transfer

This question is related to Can the theory of quantum computation assist in the miniaturization of transistors? and Is Quantum Biocomputing ahead of us? About 10 years ago, several papers discussed ...
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What is the most optimistic perspective of room-temperature solid-state QC?

I've read the "trend" article entitled Is a room-temperature, solid-state quantum computer mere fantasy? from almost 10 years ago, and was wondering if things have really changed: What is the current ...
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Can quantum computing provide advantages related to Hardware-Neural Networks?

The following question is related to this one: Will deep learning neural networks run on quantum computers?. I found it complementary and necessary because the previous answers are not completely ...
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What are the current solutions to generate entangled qubits in the solid state?

Pairs of entangled qubits (or Bell pairs, or EPR pairs) are a fundamental resource for quantum computing, in the sense that any computational platform that cannot generate entanglement will also be ...
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What is the relation between single photon qubits and squeezed light qubits?

In my constant thrill to know more about Quantum Computing I wanna know what is this relation. Additionally: Can one use squeezed light to effect multi-qubit operations on single photon qubits, or are ...
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Decoherence of spin-entangled triplet-pair states in the solid state: local vs delocalized vibrations

The context: We are in the solid state. After a photon absortion by a system with a singlet ground state, the system undergoes the spin-conserving fission of one spin singlet exciton into two spin ...
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Entanglement transfer of spin-entangled triplet-pair states between flying qubits and stationary qubits

The context: We are in the solid state. After a photon absortion by a system with a singlet ground state, the system undergoes the spin-conserving fission of one spin singlet exciton into two spin ...
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Any few-qubit versions of Lloyd's “weakly-coupled-array” quantum computing?

On 1993, Seth Lloyd published in Science a proposal for A Potentially Realizable Quantum Computer. In a nutshell, this consists in a long chain of weakly coupled qubits which are operated with (almost)...
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Is Quantum Biocomputing ahead of us?

Now that we know of bio/molecular tools that allow living organisms to deal with quantum computations e.g. the fancy proteins that allow birds to handle quantum coherence (e.g. The quantum needle of ...
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What set of quantum logical operations can one use to benchmark spin Hamiltonians?

Chemistry background: In magnetic molecules, it is sometimes the case that one can adjust the time-independent Hamiltonian by chemical design. This means there is freedom to adjust parameters in the ...
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Can one interrogate black boxes for quantum coherence?

This question is based on a scenario that is partly hypothetical and partly based on the experimental features of molecule-based quantum devices, which often present a quantum evolution and have some ...
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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,...
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What is the most economical and preferred basis for the qudit?

In Classical Simulation of Quantum Error Correction in a Fibonacci Anyon Code, the authors state on page 2 in section I. BACKGROUND - A. Topological model: We consider a system supporting ...
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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 ...
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How to store qubits while preserving Heisenberg's uncertainty principle?

I know that qubits are represented by quantum particles (for example photons) and that their state is given by one property (for example spin). My question is about the quantum memory: how are the ...
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What is the difference between transmon and Xmon qubits?

Transmon and Xmon qubits are two types of superconducting charge qubits that seem to be often used in superconducting quantum devices. However, I wasn't able to easily find direct comparisons between ...
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How are gates implemented in a continuous-variable quantum computer?

I've mostly worked with superconducting quantum computers I am not really familiar with the experimental details of photonic quantum computers that use photons to create continuous-variable cluster ...
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Do the latest D-Wave computers use Helium compounds for cooling?

Do the latest D-Wave machines use compounds of $\require{\mhchem}\ce{^{3}He}$ and $\ce{^{4}He}$ for cooling? If not, how does D-Wave approach cooling its plates low enough to achieve superconductivity?...
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Why D-Wave 2000Q requires such a low pressure?

On the D-Wave 2000Q website, it is stated that the processor environment is kept "in a high vacuum: pressure is 10 billion times lower than atmospheric pressure". Why the pressure has to be such low? ...
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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 ...
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What kinds of ions do trapped ion quantum computers use?

Trapped ion quantum computers are among the most promising approaches to achieve large-scale quantum computation. The general idea is to encode the qubits into the electronic states of each ion, and ...
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Hardware wise, how does D-Wave achieve quantum annealing?

Quantum computers have shown a new way to compute old problems. D-Wave has a quantum annealer, and Wikipedia describes the D-Wave quantum computer and its use of quantum annealing properties. ...