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Questions tagged [quantum-computer]

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.

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What happens when I input two qubits starting at state $|00\rangle$ into a hadamard gate

I was watching the following video https://www.youtube.com/watch?v=IrbJYsep45E And around 3 minutes in, they do an example computation with two qubits. The qubits started off in the state $|00\rangle$...
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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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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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Is there a general method to implement a 'greater than' quantum circuit?

I am interesting in finding a circuit to implement the operation $f(x) > y$ for an arbitrary value of $y$. Below is the circuit I would like to build: I use the first three qubits to encode $|x⟩$, ...
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Quantum Algorithm for MIMO ML detection

I am reding the paper EXIT-Chart Aided Near-Capacity Quantum Turbo Code Design by Babar et al. and in the introduction, it is stated that due to the exponentially increasing complexity of the MIMO ML ...
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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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More information about Quantum computer [closed]

1- Is it real now or not completed yet? 2- So, Can i buy one? / How many Quantum computers have been manufactured in the world? 3- Is Quantum independent (e.g Quantum+LCD+Keyboard) or it add-on ...
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Where is the problem stored in a quantum computer? [duplicate]

I am trying to develop a more intuitive understanding of quantum computing -- I suppose Feynman would tell me that’s impossible! Let’s try: if we are trying to find the minimum of a surface or ...
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Quantum Computing Research Papers, on puzzles or game theory

Are there any research papers focused on implementing a game/puzzle or game theory in Quantum Computing.
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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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1answer
100 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 ...
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1answer
70 views

How scalable are quantum computers when measurement operations are considered?

From a high-level point of view, given a quantum program, typically the last few operations are measurements. In most cases, in order to extract a useful answer, it is necessary to run multiple ...
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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 ...
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What is quantum computing vs. what is not quantum computing

That is to say, what are some common or popular misconceptions about what constitutes quantum computing? and how are those things misconceptions? It could help in explaining to frame this ...
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1answer
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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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3answers
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Example of Hamiltonian Simulation solving interesting problem?

Hamiltionian Simulation (= simulation of quantum mechanical systems) is claimed to be one of the most promising applications of a quantum computer in the future. One of the earliest – and most ...
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1answer
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Is there an intuition built on ansatz in VQE algorithm or is it more a trial and error approach?

Variational Quantum Eigensolver is a popular algorithm in Quantum Computing. But the ansatz part is very tricky. I do not really understand if they are built on some intuition, according to hardware ...
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1answer
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What is continuous quantum register and how it relates to qubits?

I would like to understand what is a continuous quantum register. I know the direct definition is a quantum register that stores a real number defined by an observable with a spectrum consisting of $\...
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Classical Memory enough to store states up to 40 qubits quantum system?

As a part of a discussion with my 'classical' friend, he insisted that making a a state machine for calculating the outcome of quantum computer is possible; so, simply calculate the outcomes of (known)...
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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 ...
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167 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 ...
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1answer
70 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 ...
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2answers
157 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 ...
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2answers
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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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3answers
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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 ...
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3answers
214 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 ...
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2answers
169 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 ...
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1answer
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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. ...
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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. ...
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2answers
120 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 ...
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3answers
177 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?
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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 ...
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2answers
145 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 ...
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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 ...
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1answer
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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 ...
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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). ...
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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 ...
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121 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?
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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 ...
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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 ...
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177 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 ...
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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 ...
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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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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 ...
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115 views

Computing with Logical Qunits

What exactly is a logical (non-physical? error corrected?) qunit? Can quantum systems be built exclusively w/ logical qunits?
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1answer
118 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 ...
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1answer
209 views

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

How is D-Wave's Pegasus architecture different from the Chimera architecture?
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14answers
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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 ...
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3answers
156 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?
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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 ...