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27 votes

What are the models of quantum computation?

The adiabatic model This model of quantum computation is motivated by ideas in quantum many-body theory, and differs substantially both from the circuit model (in that it is a continuous-time model) ...
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19 votes
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Why can't quantum annealing be described by a gate model?

A Quantum Annealer, such as a D-Wave machine is a physical representation of the Ising model and as such has a 'problem' Hamiltonian of the form $$H_P = \sum_{J=1}^nh_j\sigma_j^z + \sum_{i, j}J_{ij}\...
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18 votes

What are the models of quantum computation?

Measurement-based quantum computation (MBQC) This is a way to perform quantum computation, using intermediary measurements as a way of driving the computation rather than just extracting the answers. ...
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17 votes

Why can't quantum annealing be described by a gate model?

Annealing's more of an analog tactic. The gist is that you have some weird function that you want to optimize. So, you bounce around it. At first, the "temperature" is very high, such that the ...
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16 votes
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How does topological quantum computing differ from other models of quantum computing?

The idea of topological quantum computing was introduced by Kitaev in this paper. The basic idea is to build a quantum computer using the properties of exotic types of particles, known as anyons. ...
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12 votes
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What is the difference between quantum annealing and adiabatic quantum computation models?

Vinci and Lidar have a nice explanation in their introduction of non-stoquastic Hamiltonians in quantum annealing (which is necessary to a quantum annealing device to simulate gate model computation). ...
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12 votes
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Who built the first quantum computer using at least two qubits?

What is a qubit? And what is a quantum computer? Any claim about about which is first will depend on our definitions. One suggestion might be the 1981 experiment by Aspect, Grangier and Roger to ...
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12 votes

What are the models of quantum computation?

The Unitary Circuit Model This is the best well-known model of quantum computation. In this model one has constraints such as the following: a set of qubits initialised to a pure state, which we ...
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11 votes

What are the models of quantum computation?

Discrete-time quantum walk A "discrete-time quantum walk" is a quantum variation on a random walk, in which there is a 'walker' (or multiple 'walkers') which takes small steps in a graph (e.g. a ...
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11 votes
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Proof that any unitary can be written as $U=e^{-iH}$ with $H$ Hamiltonian with bounded norm

Since $U$ is a normal matrix, the spectral theorem applies, i.e. we can write $$ U=\sum_n\lambda_n|\lambda_n\rangle\langle\lambda_n|, $$ where $\lambda_n$ are the eigenvalues, and $|\lambda_n\rangle$ ...
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10 votes

What are the models of quantum computation?

Quantum circuits with intermediary measurements This is a slight variation on "unitary circuits", in which one allows measurements in the middle of the algorithm as well as the end, and where one ...
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9 votes
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Where can I find example circuits to learn from?

I know this is not what you are asking but this paper: Quantum Algorithm Implementations for Beginners explains the implementation of some machine learning algorithms. Hope this helps!
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8 votes

Who built the first quantum computer using at least two qubits?

It's difficult to define the point where an experimental setup is a quantum computer. But the crucial feature of a quantum computer is that it's able to perform a quantum computation. The first ...
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8 votes

What are the models of quantum computation?

Quantum annealing Quantum annealing is a model of quantum computation which, roughly speaking, generalises the adiabatic model of computation. It has attracted popular — and commercial — ...
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8 votes
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What are the fundamental differences between trapped ion quantum computers and other architectures?

Disclosure: while I am not an experimental physicist, I am part of the NQIT project, which is aiming to develop quantum hardware which is suitable to realise scalable quantum computers. The ...
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8 votes
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What good references would you recommend to understand the (continuous-variable) CV model of computation?

One of the best places to learn about the continuous-variable (CV) model is the documentation of the Strawberry Fields software for photonic quantum computing. It also includes several numerical ...
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7 votes
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In a Quantum Turing Machine, how is the decision to move along the memory tape made?

If we have a QTM with state set $Q$ and a tape alphabet $\Sigma = \{0,1\}$, we cannot say that the qubit being scanned by the tape head "holds" a vector $a|0\rangle + b|1\rangle$ or that the (internal)...
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7 votes

Is it possible to simulate a quantum computer in Virtual Reality? If yes, how?

Virtual reality in a classical computer is just a fancy front-end on top of a classical simulation. A classical computer can simulate all of the quantum physics happening inside a quantum computer, ...
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7 votes
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Anyon alternatives in topological quantum computing

Are there other instances of topological QC that do not use anyons? No, that's basically by definition. That said, there are different ways that one could use topological systems in order to achieve ...
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6 votes

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

It think the (very) short answer is that there is not a preferred platform yet. This is why there are very active research communities around each of these technologies. Often if someone says ...
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6 votes

What is the simplest algorithm to demonstrate intuitively quantum speed-up?

The difficulty with the question is the word intuitive. Intuition basically reflects our understanding of the world around us, which is described by classical physics. Quantum mechanics is exactly the ...
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6 votes
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Is quantum parallel search impossible?

The point is that free parallel computation or cloning of your existence is a wholesale misinterpretation of the concept of quantum superposition. Quantum states are analogous to probability ...
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5 votes

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

Here's a paper comparing Trapped Ion and Superconducting (the main competitors right now) from the group at UMD which compares their trapped ion system with IBM's transmon (superconducting) system. If ...
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5 votes

Is it possible to simulate a quantum computer in Virtual Reality? If yes, how?

Virtual reality is just a pretty front-end on top of a computer program. So, anything the computer program can do can be given a VR interface. As I see it, what is really being asked for is nice, yet '...
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5 votes
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What exactly are "quantum rotors"?

Quantum rotor models are quantum systems based on the quantization of systems with rotational configuration spaces. For example, a particle moving on a ring or a pendulum are rotors whose ...
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5 votes
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What does "large-scale universal quantum computation" mean?

"Large-scale" generally means that the quantum computer's ability scales to practical instances of problems. For the case of factoring, RSA keys are usually 1024/2048/4096 bit sized: if a ...
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4 votes
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Which theoretical models for quantum computing are polynomial-time equivalent?

A non-exhaustive list of theoretical models of quantum computation are provided as answers to another question: "What are the methods of quantum computation?". As to which models are polynomial-time ...
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4 votes

Is it possible to simulate a quantum computer in Virtual Reality? If yes, how?

As others have said, VR is just a way of visualizing an output from a computer. If the computer producing the output is classical, it will struggle to visualize a universal set of gates on a many ...
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