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For questions about computers that run on a quantum architecture. This is for questions about the machines themselves, not just any computing that could take place on one.

3
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2answers
58 views

Why do we need a Classical Register for carrying out Quantum Computations?

I've just started to mess about with QISKit on Python and one thing is confusing me a fair bit. Given that we are building Quantum Circuits what is the need for a classical register ? Is it because ...
5
votes
3answers
106 views

What does it mean for a quantum computer to have $X$ qubits?

I want to preface with a disclaimer that I am a physicist with minimal knowledge of computer hardware. I have a solid understanding of quantum information from a theoretical standpoint but zero ...
-2
votes
0answers
33 views

Quantum Predicate and its chain [closed]

I'm a novice in the factors that are used to explain the nature in the mechanics of the relative perception of our observation and the probe into a picture of one that is beyond our limits of physical ...
-2
votes
0answers
41 views

Quantum Computing and Imagination [closed]

Does it appear that the notion and understanding and interpretation of the notion of quantum mechanics and machines based upon principles and ideas that have surfaced from the connection and ...
4
votes
1answer
59 views

Q# factorization Method Program

Is there a method to calculate prime factorization in Q# of Visual Studio of Microsoft Quantum Development Kit? In the python language, it is the sympy.factorint ...
6
votes
2answers
125 views

Are quantum simulators like Microsoft Q# actually using quantum mechanics in their chips?

Unlike Google's Bristlecone or IBM's Qbit computer, do simulators like Q# or Alibaba really use quantum mechanics anywhere in their physical chips? Are they just defining properties using a classical ...
9
votes
2answers
154 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 ...
9
votes
3answers
101 views

Is quantum computing mature enough for a computer scientist with no physics background?

Sligthly related to this question, but not the same. Traditional computer science requires no physics knowledge for a computer scientist to be able to research and make progress in the field. Of ...
7
votes
3answers
189 views

Simplest algorithm for intuitively demonstrating quantum speed-up?

What's the simplest algorithm (like Deutsch's algorithm and Grover's Algorithm) for intuitively demonstrating quantum speed-up? And can this algorithm be explained intuitively? Ideally this would be ...
5
votes
2answers
103 views

How do you implement the Toffoli gate using only single-qubit and CNOT gates?

I've been reading through "Quantum Computing: A Gentle Introduction", and I've been struggling with this particular problem. How would you create the circuit diagram, and what kind of reasoning would ...
10
votes
0answers
61 views

Does the quantum coherence in the FMO complex have any significance to quantum computing (on a biological substrate)?

The quantum effects of the FMO complex (photosynthetic light harvesting complex found in green sulfur bacteria) have been well studied as well as the quantum effects in other photosynthetic systems. ...
5
votes
2answers
91 views

How do you represent the output of a quantum gate in terms of its basis vectors?

I'm stuck while trying to understand the Hadamard Gate in a more linear algebra understanding. (I understand the algebraic way). This is because I want to program a simulation of a quantum computer. ...
6
votes
2answers
67 views

What are the pros/cons of Trapped Ion Qubits, Superconducting Qubits and Si Spin Qubits?

Among available qubit technologies for universal quantum computing these 3 come up as promising. NV centers and Majorana qubits also underway but relatively new. I find superconducting qubits and ...
3
votes
3answers
131 views

Is it possible to purchase quantum computing hardware? [closed]

Are there schematics and/or diagrams out there to build a very basic quantum system?
2
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0answers
72 views

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 ...
6
votes
2answers
143 views

Is it possible to realize CNOT gate in 3 dimension?

CNOT gates have been realized for states living in 2-dimensional spaces (qubits). What about higher-dimensional (qudit) states? Can CNOT gates be defined in such case? In particular, is this possible ...
9
votes
3answers
701 views

Toffoli gate as FANOUT

I was searching for examples of quantum circuits to exercise with Q# programming and I stumbled on this circuit: From: Examples of Quantum Circuit Diagrams - Michal Charemza During my introductory ...
7
votes
1answer
69 views

Does a fully working quantum computer solve a specific problem at varying speeds every time?

Lets say we have a fully working quantum computer. I give it a problem to solve and measure how long it takes to solve it. I repeat the process. Would it take the exact same time to solve the same ...
6
votes
2answers
130 views

Breakthroughs in quantum computing using non-standard quanta [closed]

It seems that quantum computers can be classified by the type of quantum they operate on. Not entirely sure what category most common current systems fall into (eg. D-Wave, Google, IBM, Microsoft). ...
3
votes
2answers
186 views

Chrononic Computing (Time Evolution Systems)

In a recent question about quantum speed-up @DaftWullie says: My research, for example, is very much about "how do we design Hamiltonians $H$ so that their time evolution $e^{-iHt_0}$ creates the ...
7
votes
1answer
104 views

Is entanglement necessary for quantum computation?

Entanglement is often discussed as being one of the essential components that makes quantum different from classical. But is entanglement really necessary to achieve a speed-up in quantum computation?
5
votes
2answers
262 views

How is entanglement achieved between two particles in quantum computing?

Many texts (especially meant for public consumption) discussing quantum mechanics tend to skim over exactly how entanglement is achieved. Even the Wikipedia article on quantum entanglement describes ...
4
votes
2answers
114 views

Is running a large random brute force on quantum computer possible at the moment?

I want to run a experiment like this: Generate a bunch of random 12-character passwords like $``\texttt{<Bb\{Q,r2Qp8`}".$ Write an algorithm to randomly generate & compare value on quantum ...
7
votes
2answers
162 views

What use has quantum computing been?

Most of us on this site believe that quantum computing will work. However, let's play devil's advocate. Imagine that we suddenly hit some fundamental stumbling block that prevented further development ...
14
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6answers
442 views

If quantum speed-up is due to the wave-like nature of quantum mechanics, why not just use regular waves?

The intuition I have for why quantum computing can perform better than classical computing is that the wavelike nature of wavefunctions allow you to interfere multiple states of information with a ...
2
votes
1answer
54 views

Phononic Quantum Computing

Google returns "About 1 results" for Quantum Computing with Sound. The sole result links to an article entitled "Physicists have designed the building blocks of quantum computer that works using ...
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votes
2answers
132 views

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 using a ...
3
votes
2answers
85 views

Computing with Logical Qunits

What exactly is a logical (non-physical? error corrected?) qunit? Can quantum systems be built exclusively w/ logical qunits?
4
votes
1answer
94 views

Projection operator on Time evolution Operator

From a 9×9 Hamiltonian lying 9D space, I choose a certain subspace of 4D for designing a two qubit gate. Now the original unitary time evolution operator also lies in 9D space and it's a 9×9 size ...
6
votes
1answer
150 views

What is D-Wave's “Pegasus” architecture?

How is D-Wave's Pegasus architecture different from the Chimera architecture?
112
votes
14answers
24k views

Is quantum computing just pie in the sky?

I have a computer science degree. I work in IT, and have done so for many years. In that period "classical" computers have advanced by leaps and bounds. I now have a terabyte disk drive in my bedroom ...
6
votes
3answers
119 views

Are we certain that quantum computers 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?
5
votes
2answers
73 views

Does the no-cloning theorem impose limits on the capabilities of quantum networks?

Quantum networks or quantum internet are terms that can be found when reading about quantum computation and information nowadys, but still I they are pretty vague concepts that are still in ...
7
votes
3answers
197 views

When can we expect the first (universal) quantum computer being able to do something useful outside the academic world? [closed]

The governments, big companies (list of quantum processors) and smaller ones are in the competition of building bigger and bigger quantum computers. Not unexpectedly the number of qubits of those ...
8
votes
2answers
2k views

How many operations can a quantum computer perform per second?

I want to know what time complexity is considered efficient/inefficient for quantum computers. For this, I need to know how many operations a quantum computer can perform per second. Can anyone tell ...
9
votes
1answer
126 views

What kind of real world problems (excluding cryptography) can be solved efficiently by a quantum algorithm?

This question is very similar as Is there any general statement about what kinds of problems can be solved more efficiently using a quantum computer? But the answers provided to that questions mainly ...
8
votes
1answer
288 views

Implementing a CCCNOT gate using only Toffoli gates

A CCCNOT gate is a four-bit reversible gate that flips its fourth bit if and only if the first three bits are all in the state $1$. How would I implement a CCCNOT gate using Toffoli gates? Assume ...
9
votes
6answers
598 views

What is a qubit?

What is a "qubit"? Google tells me that it's another term for a "quantum bit". What is a "quantum bit" physically? How is it "quantum"? What purpose does it serve in quantum computing? Note: I'd ...
6
votes
3answers
104 views

Will Moore's Law be no longer effective once quantum computers are created? [duplicate]

Moore's law states that computer power doubles in every 18 months (more formally: "the number of transistors in a dense integrated circuit doubles about every two years."). Statistics suggest that ...
13
votes
2answers
111 views

Can adiabatic quantum computing be faster than Grover's algorithm?

It has been proven that adiabatic quantum computing is equivalent to "standard", or gate-model quantum computing. Adiabatic computing, however, shows promises for optimisation problems, where the ...
5
votes
1answer
62 views

How to implement a random selection of one of the 3 qubits on the IBM Q (composer)?

I would like to implement a quantum program on the IBM Composer with following characteristics: The output is the observed value of 3 qubits Only one of the 3 qubits should be observed as $1$, the 2 ...
14
votes
2answers
2k views

Is quantum cryptography safer than classical cryptography?

Quantum computing allows us to encrypt information in a different way compared to what we use today, but quantum computers are much more powerful than today's computers. So if we manage to build ...
8
votes
1answer
90 views

What is the applicability of quantum network coding?

As the title suggests, I want to know what the applicability of quantum network coding is, besides the EPR pair construction between distant pairs of 'Users-Targets'. Can quantum network coding be ...
27
votes
6answers
6k views

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 ...
6
votes
1answer
87 views

How to implement a Square root of Swap gate that swaps 2n-qubits on the IBM Q (composer)?

I am looking for an implementation using the quantum gates provided by the IBM composer of the following quantum function: input $2n$ qubits output $2n$ qubits wherein $50\%$ of the cases the state ...
4
votes
2answers
118 views

How to implement the 4 Bell states on the IBM Q (composer)?

I would like to simulate the 4 "Bell States" on the IBM composer? How can I best implement those 4 Bell states using the existing set of gates ? Here below you see the definition of the 4 Bell ...
7
votes
2answers
110 views

Practical Implementations of QECCs in IBM Q Experience

I am learning how to program the IBM Q Experience quantum computers in order to learn more about how does it work and in order to perform some experiments in it. By doing so I was wondering what are ...
5
votes
1answer
40 views

Reference on MITxPRO Applications of Quantum Computing Professional Certificate Program

Recently I found out the Applications of Quantum Computing Professional Certificate Program that MITxPRO is offering for people interested in quantum computing. I saw that it is consisted of four ...
7
votes
2answers
393 views

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,...
13
votes
3answers
2k views

What integers have been factored with Shor's algorithm?

Shor's algorithm is expected to enable us to factor integers far larger than could be feasibly done on modern classical computers. At current, only smaller integers have been factored. For example, ...