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21
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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 objective is to minimise (or maximise) a function…
Dyon J Don Kiwi van Vreumingen
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21
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Why are quantum gates unitary and not special unitary?
Given that the global phases of states cannot be physically discerned, why is it that quantum circuits are phrased in terms of unitaries and not special unitaries? One answer I got was that it is just for convenience but I'm still unsure.
A related…
wdc
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21
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What would a very simple quantum program look like?
After reading the "first programmable quantum photonic chip". I was wondering just what software for a computer that uses quantum entanglement would be like.
Is there any example of code for specific quantum programming? Like pseudocode or…
Didix
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21
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How to measure in another basis
I am new to qiskit and I have to simulate a quantum circuit. I read this documentation https://qiskit.org/textbook/ch-states/single-qubit-gates.html where it is left as an exercise to the reader to write a function to measure in the $|+i\rangle$ and…
thedumbkid
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What is the current state of the art in quantum sorting algorithms?
As a result of an excellent answer to my question on quantum bogosort, I was wondering what is the current state of the art in quantum algorithms for sorting.
To be precise, sorting is here defined as the following problem:
Given an array $A$ of…
Discrete lizard
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21
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Level of advantage provided by annealing for traveling salesman
My understanding is that there seems to be some confidence that quantum annealing will provide a speedup for problems like the traveling salesman, due to the efficiency provided by, ex, quantum tunneling. Do we know, however, around how much of a…
auden
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Why are non-Clifford gates more complex than Clifford gates?
There are two groups of quantum gates - Clifford gates and non-Clifford gates.
Representatives of Clifford gates are Pauli matrices $I$, $X$, $Y$ and $Z$, Hadamard gate $H$, $S$ gate and $CNOT$ gate. Non-Clifford gate is for example $T$ gate and…
Martin Vesely
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20
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Reference that explains how to read 3d topological diagrams for surface code computations
I like making diagrams to describe computations. For the surface code, an excellent tool is 3d topological diagrams. Here is an example diagram (made by me in SketchUp):
The basic idea is that white boundaries are places where Z observable chains…
Craig Gidney
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Can a quantum computer easily determine the mixing time of the Rubik's cube group?
Officials in Rubik's cube tournaments have used two different ways of scrambling a cube. Presently, they break a cube apart and reassemble the cubies in a random order $\pi\in G$ of the Rubik's cube group $G$. Previously, they would apply a random…
Mark Spinelli
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No-cloning theorem and distinguishing between two non-orthogonal quantum states
I'm currently reading Nielsen and Chuang's Quantum Computation and Quantum Information and I'm not sure if I correctly understand this exercise (on page 57) :
Exercise 1.2: Explain how a device which, upon input of one of two non-orthogonal quantum…
TheAmazingKitchen
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What does "measurement in a certain basis" mean?
In the Wikipedia article about Bell states it is written:
Independent measurements made on two qubits that are entangled in Bell states positively correlate perfectly, if each qubit is measured in the relevant basis.
What does it even mean to…
user72
20
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2 answers
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 the environment-assisted quantum walks in…
agaitaarino
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What does it mean for two qubits to be entangled?
I have done some sort of online research on qubits and the factors making them infamous i.e allowing qubits to hold 1 and 0 at the same time and another is that qubits can be entangled somehow so that they can have related data in them no matter how…
Arshdeep Singh
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Alternative to Bloch sphere to represent a single qubit
In order to represent the single qubit $|\psi\rangle$ we use an unitary vector in a $\mathbb{C}^2$ Hilbert space whose (one of the) orthonormal base is $(|0\rangle, |1\rangle)$.
We can draw $|\psi\rangle$ using a Bloch ball. However, I found this…
incud
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Do multi-qubit measurements make a difference in quantum circuits?
Consider the unitary circuit model of quantum computation. If we need to generate entanglement between the input qubits with the circuit, it must have multi-qubit gates such as CNOT, as entanglement cannot increase under local operations and…
Kiro
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