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Questions tagged [architecture]

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

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8 votes
2 answers
616 views

What design considerations set the frequency bounds for superconducting qubits?

Superconducting qubits generally have frequencies within the range of 4 - 8 GHz. What design considerations give the upper and lower bounds for what is a feasible design. I.e, why can't they be higher ...
10 votes
0 answers
213 views

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 ...
0 votes
0 answers
28 views

How can I get the structure of the variational ansatz for VQLS?

I have got a system of linear equations $$ A|x \rangle = |b\rangle \\ A = 0.45Z_3 + 0.55I \\ |b\rangle = H_1 H_2 H_3 $$ and I would like to solve it for $|x\rangle$. I am currently trying to ...
4 votes
3 answers
777 views

Are there qudit systems, and why are they not as popular as qubit systems?

Qudit is a $d$-level system that generalizes a qubit. From what I understood qudits are more resource efficient when it comes to spanning the state space. If $N$ is a dimension of a state space, then ...
12 votes
2 answers
702 views

How are elementary quantum gates realised?

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 "...
44 votes
3 answers
10k views

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 ...
7 votes
1 answer
310 views

Are indistinguishable bosons and fermions computationally equivalent to distinguishable qubits?

From the middle-late decades of the last century, many researchers such as Bennett, Benoif, Deutsch, Feynman, Manin, Wiesner, among others, had some intuition that qubits are computationally more ...
1 vote
0 answers
46 views

If the main challenges limiting quantum computing's abilities will be passed, will even video games be run on quantum computers?

I'm terribly sorry for my lack of knowledge in (quantum) computer architecture, I still need to learn a lot. But I'd like to know whether quantum computers can execute the same tasks (like running a ...
25 votes
3 answers
3k views

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 ...
17 votes
2 answers
3k 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 ...
2 votes
0 answers
43 views

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 ...
1 vote
0 answers
52 views

Are there any quantum standards already in development and accessible as draft documents?

Are there any quantum standards already in development and accessible as draft documents? Any documents describing standardized way of describing and ensuring common meaning/interoperability, like e.g....
1 vote
1 answer
203 views

Gate times for photonic quantum computers

I am trying to understand the landscape of one- and two-qubit gate times for various quantum computing architectures. It is not so hard to find gate times for various gates such as Hadamard, CNOT and ...
2 votes
1 answer
272 views

Good review articles on microwave hardware for superconducting qubit quantum computing?

I am trying to find some review articles on the microwave hardware used in superconducting qubit quantum computing. So far, most papers that I found seem to be high level overviews, e.g., Multilayer ...
2 votes
1 answer
57 views

Questions on Definitions and Concepts Regarding Toric Codes

Currently, I reading the toric code section in the beginning of the paper Topological Quantum Memory. Here are a couple of sections that are somewhat confusing to me. (1) This quote below is under a ...
3 votes
1 answer
176 views

A Particular Way of Erasing Ancilla Qubits

I am currently reading the paper Topological Quantum Memory by Dennis, Kitaev et. al. My main interest is to conceptually understand the idealized assumptions / requirements of a quantum computer ...
9 votes
2 answers
337 views

Is there a good reason to use T-count minimization for circuits executed on current IBM open quantum systems (real hardware)?

As far as I understood from a series of papers, minimizing the T-count in Clifford+T circuits is essential for fault-tolerant ...
19 votes
2 answers
467 views

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 ...
3 votes
1 answer
1k views

What constitutes a quantum database?

Newb question, I know it's broad. I'm coming here for validated pointers, so I can know what to read. I have QT for CS (Yanofsky, Mannucci) and am reading about Shannon and Von Neumann entropy, but I'...
1 vote
1 answer
1k views

What are the pros and cons of the most popular QC architectures?

I notice numerous companies and research groups around the world trying to build QC's with wildly different approaches. Intuitively, this suggests to me that QC is still very early in its maturation - ...
5 votes
1 answer
139 views

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 ...
2 votes
0 answers
81 views

Usefulness of having a cryogenic controller at 4K for transmons/spin qubits

There have been plenty of papers on the design of cryogenic control chips working at ~4K for qubit control and readout. These papers talk about how running coaxial cables from room temperature control ...
5 votes
1 answer
161 views

Can we calculate the quantum volume of a classical computer?

The quantum volume is typically taken as a popular metric to determine the capability of a quantum computer to solve complex problems. Since the end goal is to develop quantum computers that can solve ...
8 votes
1 answer
195 views

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 ...
21 votes
3 answers
2k views

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 ...
1 vote
1 answer
89 views

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 ...
2 votes
0 answers
21 views

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 $...
9 votes
2 answers
588 views

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 ...
3 votes
2 answers
567 views

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 nonabelian ...
14 votes
2 answers
3k views

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 ...
2 votes
0 answers
128 views

Solution for the "Input and Output theory" for circuit/cavity-QED Quantum Architecture [closed]

This question consists of the basic calculations which are often referred to as "trivial" in most references in circuit-QED. However, are not so trivial for anyone who starts fresh into the ...
1 vote
0 answers
39 views

A distributed, scale-out quantum computing architecture?

Having been part of the mainframe, client-server, and now containers scale out architecture, I can observe the parallel and resemblance of today's quantum computers (massive) to that of the mainframe ...
4 votes
0 answers
62 views

What is the executable opcode for Qiskit quantum hardware, as the quantum circuits or the transpiled/compiled QObj/ QASMQObj are assembly languages? [duplicate]

When we write a QASM code or build quantum circuit on Qiskit GUI, it converts it into QObj/QASMQObj (refering paper Qiskit Backend Specifications for OpenQASM and OpenPulse Experiments) or its ...
12 votes
0 answers
128 views

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 ...
5 votes
1 answer
139 views

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. ...
2 votes
1 answer
108 views

What determines the topology/connectedness of quantum computers?

Some quantum computers hold their qubits in a 2D array. I've even seen a 1D topology I think. On IBM Q, you can see which qubits talk to which qubit. I would like to know what determines/limits the ...
3 votes
3 answers
451 views

Why don't quantum computing scientists build two 50-qubit processors and connect them in parallel instead of building one 100-qubit processor?

Isn't it more scalable to build multiple processors of a lower qubit and connect them in parallel instead of building one processor of a higher qubit?
5 votes
6 answers
8k views

How to build a quantum computer in your house?

As still quarantine is going on for some of us. I was wondering how to make a Quantum Computer in your garage. What may be the total cost for building one? Was inspired by this youtube video.
2 votes
0 answers
28 views

What are the practical limitations of complementing quantum computations with memristors?

Considering the current state of research into quantum memristors, and the advantages/disadvantages of quantum and memristor driven computing architectures: Quantum Memristors Quantum Memristor ...
2 votes
2 answers
178 views

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 ...
3 votes
1 answer
159 views

Is quantum computing the most advanced computing technology we will ever have? [closed]

Is there already evidence today (e.g. basic theoretical research or even prototypes) on what the next technolgy will be/could be that is superior to quantum computers? Or have we reached the "...
2 votes
1 answer
95 views

Mightn't the cost of a quantum computer be lowered by building it on earth sans cooler and then using it in the frigid vacuum of space?

I'm picturing the control equipment on the inside of an ISS wall with the part that needs being cold being on the outer side. I imagine this has been considered and if so, was the idea rejected for ...
2 votes
1 answer
88 views

Are all the IBM QX mapping bidirectional?

The connection between physical qubits of IBM devices are all bidirectional or there are some architectures that there existing some unidirectional connection? I found that in IBM Quantum experience, ...
6 votes
1 answer
1k views

What is the state of the art on Quantum Random Access Memories? [duplicate]

I realized that Quantum Random Access Memory (qRAM) was proposed to make quantum computers more similar to classical one. Currently quantum computers have very constrained memory, given only quantum ...
3 votes
2 answers
188 views

Why IBM devices have the same number of qubit and the same architecture, but the error rates are different?

Here are two different IBM quantum online devices, Both of them have the 5 qubits and the same architectures. But why do they have different error rate? What's the different between them?
1 vote
0 answers
66 views

What are the general hardware components of a universal quantum gate computer?

Although the architecture of a quantum computer depends on the implemented qubit system, I still wonder what the general structure of hardware parts would be. Evidently, a quantum computer isn't ...
4 votes
1 answer
1k views

Why are superconducting qubits the most popular approach to build a quantum computer?

There are many different physical implementations of qubits: NMR, spin qubit, N color center in diamond, superconducting qubit, trapped ions, photonics quantum computing, topological qubit, etc. ...
0 votes
0 answers
52 views

How many types of quantum computers are currently being researched? [duplicate]

I came across a "new" type of quantum computer - photonic quantum computing. Is this type of technology of interest here? You may read about an example here. I wonder how many types of quantum ...
6 votes
2 answers
422 views

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 ...
5 votes
1 answer
402 views

What are the physical reasons behind noise/errors in quantum computers?

We know that the current quantum computers are noisy/error-prone. They are susceptible to gate errors (single qubit and multi-qubit), decoherence (relaxation and dephasing), readout error, etc. I want ...