2
votes
1answer
11 views

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)...
3
votes
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 ...
3
votes
1answer
75 views

Can we process infinite matrices with quantum computer?

Can we process infinite matrices with quantum computer? If then, how can we do that?
7
votes
1answer
74 views

Significance of Clifford operations from quantum error correction perspective

In the literature on QECC, Clifford gates occupy an elevated status. Consider the following examples which attest to this: When you study stabilizer codes, you separately study how to perform ...
7
votes
1answer
82 views

How would a quantum computer be used to solve Partial Differential Equations?

Say you have a PDE you want to solve. What kind of quantum algorithms would you use to solve it? How do we input our problem on a quantum computer? What will be the output and in what form? I know ...
2
votes
2answers
66 views

Finding the maximum number of Q# simulatable qubits

I'm new to Q# and I was curious on how one would find the number of Q# simulatable qubits for a specific machine. I know Microsoft has an approximation of 16GB ~ 30 qubits but I wanted a better ...
4
votes
2answers
106 views

What exactly are “quantum rotors”?

The Wikipedia entry on the subject is rather short. I am also curious about generalizations of quantum rotors in n-dimensions. An introductory explanation with at least one resource for further ...
-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
2answers
53 views

Simplifying Quantum Tensor products with coefficients

$\newcommand{\ket}[1]{\lvert#1\rangle}$I am trying to show equality of two intermediate steps in the rearrangement of the Quantum Fourier transform definition, but I do not know how to rearrange the ...
3
votes
1answer
52 views

Is there a Hamiltonian simulation technique implemented somewhere?

I was wondering if there was some code available for Hamiltonian simulation for sparse matrix. And also if they exist, they correspond to a divide and conquer approach or a Quantum walk approach?
3
votes
1answer
48 views

What about BosonSampling can be publicly verified?

Boson Sampling, sometimes stylized as BosonSampling, is an attractive candidate problem to establish quantum supremacy; the engineering problems appear more surmountable than those associated with a ...
3
votes
1answer
42 views

How to calculate the off-diagonal elements of a density matrix using the measurement result?

For example, one have measured some states like $|0\rangle$ in the computational basis for many times and got the approximate probability of getting 0 and 1 ($P(0)$ and $P(1)$). Then how does he ...
6
votes
1answer
41 views

How are magic states defined in the context of quantum computation?

Quoting from this blog post by Earl T. Campbell: Magic states are a special ingredient, or resource, that allows quantum computers to run faster than traditional computers. One interesting example ...
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
1answer
60 views

What exactly is “Random Circuit Sampling”?

Many people have suggested using "Random Circuit Sampling" to demonstrate quantum supremacy. But what is the precise definition of the "Random Circuit Sampling" problem? I've seen statements like "the ...
6
votes
2answers
50 views

What exacty is “matrix sparsity” $s$?

In many sources (like on Page 30 here), I found that the complexity of the original Harrow Hassidim Lloyd is stated as $\mathcal{O}(\log (N) s^2 \kappa^2/\epsilon)$ where $s$ is said to be the "matrix ...
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 ...
6
votes
1answer
60 views

Does the need of many quantum algorithms to be repeated several times impair the efficiency gains?

As I understand so far, in some algorithms such as Simon's algorithm, swap-test algorithm or quantum k-means algorithm, we repetitively perform a measurement yielding a classical result. Consequently, ...
5
votes
0answers
33 views

Quantum Belief Propagation decoding

I have been reading about a family of quantum error correction codes called Quantum Turbo Codes, which are the quantum analog of the well-known classical Turbo codes. This codes were introduced in ...
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 ...
6
votes
3answers
140 views

What is the difference between $\vert 0 \rangle + \vert 1 \rangle$ and $\vert 0 \rangle \langle 0 \vert + \vert 1 \rangle \langle 1 \vert$?

In a discussion with Jay Gambetta on the QISKit Slack channel, Jay told me that "T2 is the time that $\vert 0 \rangle + \vert 1 \rangle$ goes to $\vert 0 \rangle \langle 0 \vert + \vert 1 \rangle \...
8
votes
2answers
146 views

Quantum Algorithms for Convolution

I was looking into applications of Quantum Computing for machine learning and encountered the following pre-print from 2003. Quantum Convolution and Correlation Algorithms are Physically Impossible. ...
8
votes
1answer
56 views

Minimum number of CNOTs for a 4-qubit increment on a planar grid

Recently I've been wondering how high NISQ machines will be able to "count". What I mean by that is, given the most optimized increment circuit you can make, how many times can you physically apply ...
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 ...
3
votes
2answers
56 views

Combining Different Qunits

Has any work been done on quantum systems which use a combination of types of qunits (eg. using qubits & qutrits simultaneously)? If work has been done, what kind of work has been done? (eg. in ...
5
votes
2answers
170 views

Inner product of a quantum states

I found an algorithm that can compute the distance of two quantum states. It is based on a subroutine known as swap test (a fidelity estimator or inner product of two state, btw I don't understand ...
6
votes
2answers
92 views

Just want to confirm: Do two CNOT gates cancel each other?

I see somewhere that this happens: But I wonder if this is just identity.
6
votes
1answer
161 views

Quantum Algorithm for God's Number

God's number is the worst case of God's algorithm which is a notion originating in discussions of ways to solve the Rubik's Cube puzzle, but which can also be applied to other combinatorial puzzles ...
7
votes
2answers
75 views

Minimum number of CNOTs for Toffoli with non-adjacent controls

I want to decompose a Toffoli gate into CNOTs and arbitrary single-qubit gates. I want to minimize the number of CNOTs. I have a locality constraint: because the Toffoli is occurring in a linear array,...
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 ...
6
votes
0answers
37 views

Resources for quantum biology

Are there any books, courses, tutorials, etc. for studying quantum biology? Preferably they provide some introduction/primer on the relevant quantum aspects of the quantum biological systems being ...
-1
votes
1answer
54 views

Hilbert space to accurately represent Rubik's Cube

What Hilbert space of dimension greater than 4.3e19 would be most convenient for working with the Rubik's Cube verse one qudit? The cardinality of the Rubik's Cube group is given by: Examples 66 ...
5
votes
3answers
361 views

Advantange of Hadamard gate over rotation about the X axis for creating superpositions

When I look at most circuits (admittedly small sample as I'm a beginner), the Hadamard gate is used a lot to prepare a superposition from say the $\mid0\rangle$ state. But upon a little reflection, we ...
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 ...
6
votes
2answers
105 views

Is there a tool that can give you the unitary representing a quantum circuit from just a string?

Say I have a string representing the operations of a quantum circuit. I want to have the unitary operator representing it. Is there a tool for doing so in Python or else?
3
votes
2answers
92 views

How do we code the matrix for a controlled operation knowing the control qubit, the target qubit and the $2\times 2$ unitary?

Having n qubits, I want to have the unitary described a controlled operation. Say for example you get as input a unitary, an index for a controlled qubit and another for a target. How would you code ...
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. ...
10
votes
2answers
101 views

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 ...
5
votes
2answers
375 views

Incorrectly Calculating Probability Amplitudes for 3-qbit Circuit

I’m trying to calculate the probability amplitudes for this circuit: My Octave code is: ...
7
votes
2answers
108 views

Can we perform quantum mechanical simulations using a quantum computer?

I'm a computer science major who's really keen on physics and quantum mechanics. I have started learning about Q# and D-Wave, but I just wanted to know if it's possible to test quantum mechanical ...
4
votes
6answers
235 views

Good metaphors for n-level quantum systems

It seems that a coin flip game is a decent metaphor for a 2-level system. Until 1 of the 2 players picks heads or tails, even if the coin has already been flipped, the win/loss wave form has not yet ...
-2
votes
1answer
126 views

Can D-Wave optimize yacht design with all possible formulas and CFD and give me thousands of designs? [closed]

Yacht design is hull, resistance, wave making, near-field far-field wake, side pressure, velocity prediction program, stability and simple computational fluid dynamics, sail design etc. There are ...
6
votes
2answers
312 views

Possibility of a “reset” quantum gate

I wish to have a "reset" gate. This gate would have an effect to bring a qubit to the $\mid0\rangle$ state. Clearly, such a gate is not unitary (and so I'm unable to find any reliable implementation ...
2
votes
4answers
127 views

Are classical bits quantum?

A bit is a binary digit, typically 0 or 1. Until a value is assigned (or a measurement is made) a bit is in a superposition of the entangled binary pair, is it not?
3
votes
2answers
94 views

Comparing run times on IBM Quantum Experience

I have run this program - ...
5
votes
1answer
82 views

What are the preferred numerical methods to simulate the evolution of a state through a time-dependent Hamiltonian?

Under the influence of a time-independent Hamiltonian $H$, a state $|\psi\rangle$ will evolve after a time $t$ to the final state $|\psi(t)\rangle=e^{-iH t}|\psi\rangle$, while in the most general ...
7
votes
2answers
92 views

Resources for Quantum Communication Complexity

I recently came to know about this interesting topic of "communication complexity". In simple words, Wikipedia defines it as: In theoretical computer science, communication complexity studies the ...
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. ...

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