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What precisely is quantum annealing?
Many people are interested in the subject of quantum annealing, as an application of quantum technologies, not least because of D-WAVE's work on the subject. The Wikipedia article on quantum annealing implies that if one performs the 'annealing'…
Niel de Beaudrap
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31
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What is the difference between quantum annealing and adiabatic quantum computation models?
From what I understood, there seems to be a difference between quantum annealing and adiabatic quantum computation models but the only thing I found on this subject implies some strange results (see below).
My question is the following: what is…
Adrien Suau
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What is the difference between superpositions and mixed states?
My understanding so far is: a pure state is a basic state of a system, and a mixed state represents uncertainty about the system, i.e. the system is in one of a set of states with some (classical) probability. However, superpositions seem to be a…
Norrius
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When will we know that quantum supremacy has been reached?
The term "quantum supremacy" - to my understanding - means that one can create and run algorithms to solve problems on quantum computers that can't be solved in realistic times on binary computers. However, that is a rather vague definition - what…
blalasaadri
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5 answers
How can I implement an n-bit Toffoli gate?
I want to create a Toffoli gate controlled by n qubits, and implement it in QISKit. Can this be done? If so, how?
Ali Javadi
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How does measurement of one qubit affect the others?
To represent a quantum computer's state, all the qubits contribute to one state vector (this is one of the major differences between quantum and classical computing as I understand it). My understanding is that it's possible to measure only one…
auden
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29
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2 answers
Circuit construction for Hamiltonian simulation
I would like to know how to design a quantum circuit that given a Hermitian matrix $\hat{H}$ and time $t$, maps $|\psi\rangle$ to $e^{\frac{i\hat{H}t}{\hbar}} |\psi\rangle$ with $\hbar =1$.
Thank you for your answer.
Gradius
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Why can't there be an error correcting code with fewer than 5 qubits?
I read about 9-qubit, 7-qubit and 5-qubit error correcting codes lately. But why can there not be a quantum error correcting code with fewer than 5 qubits?
Aleph
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Are quantum computers just a variant on Analog computers of the 50's & 60's that many have never seen nor used?
In the recent Question "Is Quantum Computing just Pie in the Sky" there are many responses regarding the improvements in quantum capabilities, however all are focussed on the current 'digital' computing view of the world.
Analog computers of old…
Philip Oakley
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5 answers
Does Moore's law apply to quantum computing?
Plain and simple. Does Moore's law apply to quantum computing, or is it similar but with the numbers adjusted (ex. triples every 2 years). Also, if Moore's law doesn't apply, why do qubits change it?
Alex Jone
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Is there any potential application of quantum computers in machine learning or AI?
A lot of people believe that quantum computers can prove to be a pivotal step in creating new machine learning and AI algorithms that can give a huge boost to the field. There have even been studies that our brain may be a quantum computer, but so…
Piyush Kathuria
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4 answers
Is error correction necessary?
Why do you need error correction? My understanding is that error correction removes errors from noise, but noise should average itself out. To make clear what I'm asking, why can't you, instead of involving error correction, simply run the…
auden
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28
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1 answer
How to understand the Haar measure from a quantum information perspective?
I found it a little difficult to understand it using Wikipedia and some mathematical documents. How to understand the Haar measure from a quantum information theory perspective? Are there any materials that explain it?
raycosine
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4 answers
How to calculate circuit depth properly?
Is the circuit depth the longest sequence of gates applied on one of the qubits?
Or is it something more complicated?
C-Roux
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Why does the "Phase Kickback" mechanism work in the Quantum phase estimation algorithm?
I've probably read the chapter The quantum Fourier transform and its applications from Nielsen and Chuang (10 th anniversary edition) a couple of times before and this took this thing for granted, but today, when I looked at it again, it doesn't…
Sanchayan Dutta
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