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Minimum number of ancilla qubits required to make a transformation unitary?

Background The counterpart of a NOT gate is the CNOT gate. They make use of ancilla qubits to achieve this. Question Given an arbitrary non-unitary transformation what are the minimum number of ...
1
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1answer
22 views

IBM Q experience - error code 520

I have been running a variational circuit optimizing the parameters on the "melbourne" device. The system launches multiple jobs in parallel, and only gets the jobs accepted that my credit allows. The ...
0
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1answer
16 views

Find the Q-Experiment tutorial for beginner

Where I can find the previous Quantum-Experiment tutorial for beginners? (the one that was under https://quantumexperience.ng.bluemix.net/qstage/#/account)
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0answers
19 views

What does the error rate on the IBMQ website mean?

How is the error rate pointed by the arrow defined? How did you get it? thanks!
1
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1answer
30 views

Quantum random number generator

Can we generate quantum random numbers through Qiskit? I want to try the random number generator without using optics or noise.
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0answers
15 views

OpenPulse: Where to get current pulse definitions for standard gates?

Is backend.defaults().cmd_def and backend.defaults().pulse_library kept updated regularly? Is this the correct place to pull the best calibrated pulses for the standard gates? I am working on a ...
2
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1answer
36 views

How is a quantum computer programmed?

After lightly reading into quantum algorithms and the hardware of quantum computers, I subsequently started wondering how a quantum computer is programmed so it executes the desired quantum algorithm ...
3
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1answer
50 views

Getting a layout for qubits in Qiskit

I'm trying to use Qiskit's built in transpiler passes to do the following. I would like to take a quantum circuit and allocate the logical qubits to physical qubits. The tutorial doesn't really ...
2
votes
1answer
18 views

How many iterations does Grover’s search need to find one out of $M$ marked items?

How many iterations are needed in Grover’s quantum search for finding one out of M marked items in a database containing N items (for 1 < M < N/2)? I would have thought we just reduce the size ...
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0answers
10 views

How's quantum noise and fault-tolerance related to symplectic geometry and geometric quantization?

Gil Kalai often speaks of the apparent connection between symplectic geometry, geometric quantization, and quantum noise. He is known to describe one of his focus areas as: (...) properties and ...
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1answer
47 views

What can be done so far with cloud quantum computing?

As a developer myself, I still do not understand what can be done so far with services like AWS BRAKET or IBM CLOUD QUANTUM COMPUTING. Can someone explain me the practical purpose of it in the present?...
3
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1answer
45 views

How to obtain the tensor-product of two quantum operations (superoperators) explicitly?

I have an amplitude damping channel, denoted as a superoperator $\mathcal{E}$ with operator elements \begin{matrix} E_1=\begin{pmatrix} 1 & 0 \\ 0 & \sqrt{1-r} \end{pmatrix},\quad ...
3
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0answers
39 views

Can quantum entanglement be expressed in terms of knot theory?

While writing this answer I was wondering whether the analogy of the nature of entanglement in the GHZ state with Borromean rings is more than a mere analogy (cf. Aaronson's lecture). The question ...
3
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1answer
49 views

Understanding the monogamy of entanglement with respect to GHZ States

Given the GHZ state wrt n = 3: $\frac{|000⟩ + |111⟩}{\sqrt{2}}$, I'm trying to understand how the principle of monogamy of entanglement manifests here. I came across this explanation. Let’s say ...
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1answer
40 views

Bloch sphere and quantum operations [closed]

Evidently the Bloch Sphere is used as a graphical representation for any single qubit system, although what does it mean at an intuitive level? Moreover, the manipulation of qubits still seems unclear,...
5
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1answer
46 views

How to prepare Unitary Coupled Cluster ansatz for VQE in a circuit?

I have read the following paper by Dumitrescu et al. To make a Unitary Coupled Cluster (UCC) ansatz, one prepares with the following equation. $$ | \psi_{\rm{UCC}} \rangle = U(\theta)|\mathrm{HF}\...
2
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1answer
51 views

How to specify the CNOT gate direction (control qubit to target qubit) in Qiskit?

If I act a CNOT gate on quantum circuit: from qiskit import QuantumCircuit qc = QuantumCircuit(2, 2) qc.cx(0, 1) it means that qubit_0 is the control qubit, and ...
2
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0answers
22 views

Self reducibility of QCMA problems

Self reducibility is when search version of the problems in a language reduce to decision versions of the same problems. NP-complete problems are self reducible. Are QCMA complete problems self ...
2
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1answer
48 views

Is there a way to output a circuit from Qiskit to the IBM Q Experience circuit composer?

I can't seem to find anything, but this seems like something that should be possible.
2
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2answers
106 views

Interpretations of quantum computing power [closed]

Over the years I encountered different explanations of quantum computing advantage over classical computers. But I am not sure which explanations are in fact valid and which are not. Quantum ...
4
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2answers
78 views

How to construct the unitary representation of the function $f(x, y, z) = (x \oplus y, y \oplus z)$?

Consider the function $f:\{0, 1\}^3\to\{0, 1\}^2$ with $f(x, y, z) = (x \oplus y, y \oplus z)$. How would you construct its standard unitary representation?
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5answers
991 views

Resources to study quantum algorithms and quantum complexity

I have a computer science background, and I'm interested in studying 'quantum algorithms' and anything that is related like 'quantum complexity'. I would like to have all important resources that is ...
3
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0answers
23 views

How does batching work in the optimizer loop of the VQC algorithm in Qiskit Aqua?

I've playing around with a binary classification problem with a dataset of size 1000 examples and 5 features. I'm using the VQC algorithm from the Qiskit package the that uses a feature map and a ...
1
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0answers
40 views

Ripple Adder using Full Adder [closed]

I have been trying to implement a ripple carry adder using qsikit in IBM Q Experience. I was able to implement full carry adder but I am having trouble with ripple carry adder. I am able to add 100 + ...
5
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1answer
77 views

Why are multiple quantum gates, in a quantum circuit, used?

After reading about quantum computers, for a high school research paper, a few questions arose concerning quantum logic gates. At first, it seems that quantum logic gates are in essence various ...
1
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1answer
31 views

How to create a q# operation to generate a random number from 1 to max?

I have the following problem: I want to create a q# operation for generating a random integer from 1 to max and return the generated number. What algorithm do I need? What does the q# code look like? ...
5
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1answer
202 views

Understanding quantum teleportation algorithm from qiskit tutorials

I am very new to quantum computing and I have recently started to experiment with qiskit module in python, by following tutorials and implementing simple algorithms....
2
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0answers
43 views

Please clarify the following orthogonal property (quantum anonymous voting)

I am a beginner at QC, currently going through a paper on Quantum Anonymous Voting. Please clarify the orthogonal property described in the following scenario. Consider $n$ voters $V_{0}, V_{1}, V_{2}...
1
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1answer
42 views

Can't access IBMQ (NameError: name 'IBMQ' is not defined)

When I type this: IBMQ.load_account(), I am getting this error. What does this mean, and how can I rectify it? ...
1
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1answer
38 views

Density matrix for a diagonally polarized photon

I am struggling with the density matrix for diagonally polarized photons. Can I think of diagonally polarized photons as a mixture of vertically and horizontally polarized photons?
0
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0answers
40 views

How many types of quantum computers are currently being researched? [duplicate]

I came across a "new" type of quantum computer - photonic quantum computing. Is this type of technology of interest here? You may read about an example here. I wonder how many types of quantum ...
1
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0answers
24 views

What authentication protocol to use for BB84 and other QKD protocols?

Just like other classical and quantum key distribution protocols, BB84 is vulnerable to "man"-in-the-middle attacks, where Eve pretends to be Bob to Alice, and Eve pretends to be Alice to Bob. The ...
2
votes
1answer
54 views

Quantum tomography on two qubits

I would like to do a quantum tomography on two q-bit state. Recently, I successfully did so for one q-bit based on Nielsen-Chuang. They advise to use this formula for one q-bit density operator ...
2
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0answers
24 views

Grover's search for solving TSP

Consider the modified version of the Traveling Salesman Problem where you are searching for a path of length lass than some $k$. We can solve this problem using Grover's search where we encode each ...
2
votes
1answer
77 views

How to measure one of the qubits in a two-qubit register?

How do I measure the first qubit of an entangled vector, say \begin{pmatrix} 1 \\ -1 \\ 0 \\ 0 \\ \end{pmatrix} is what I get on the end of Deutsch's algorithm. If I get it right, I should now ...
4
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1answer
50 views

How should I interpret $|2\rangle|3\rangle$?

I am a beginner at QC. I was going through the basics of multi-qubits I encountered a state $|2\rangle|3\rangle$. I want clarification on the following points: Can I write $|2\rangle$ as $|10\...
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2answers
113 views

Is quantum superposition state a truth or an assumption?

Please, be patient with my question I already read that there is a heuristic that makes superposition a fact of reality. In addition, this superposition, when observed, it has a state of 0 or 1. ...
2
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0answers
40 views

How to generate the following $n$-level $n$-particle singlet state? [duplicate]

Could you please give a direction/reference towards realising the following using any set of realisable quantum gates $$\boxed{|S_{n}\rangle = \frac{1} {\sqrt{n!}} \sum_{S\in P_n^{n}} ( \,-1) \,^{\...
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2answers
80 views

Does this setup violate relativity?

Suppose Alice needs to transmit a bit of information about something which happened just before $t = 0$ to Bob who is light years away from Alice. Entangled pairs of qubits, $\left|00\right> + \...
1
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1answer
48 views

Color-Space as Effective and Intuitive Qutrit Physical Realization?

Has anyone used or considered color-space and color superposition for Qutrit work? A classical color-sphere has black and white at its poles, a grey scale as its axis, pure spectral colors as a color-...
4
votes
1answer
52 views

Where does error correction go in a quantum algorithm?

Where does QEC fit in the larger picture of the execution of a fault tolerant quantum algorithm? For QEC, there is an initial preparation of the qubit state and the ancillary qubits; then a "noisy ...
2
votes
1answer
39 views

Mightn't the cost of a quantum computer be lowered by building it on earth sans cooler and then using it in the frigid vacuum of space?

I'm picturing the control equipment on the inside of an ISS wall with the part that needs being cold being on the outer side. I imagine this has been considered and if so, was the idea rejected for ...
1
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1answer
43 views

How can one trapped ion physically represent quantum states?

I don't understand this "trapped ion (qubit implemented by the internal state of trapped ions)" One qubit implemented by the internal state of trapped ions (plural)? "Consider an ion trap. The ions ...
2
votes
1answer
38 views

Couldn't connect to IBMQ server

When I access IBM Q backend with qiskit code, an error occurs. from qiskit import IBMQ qt = 'xxxxxxxxx' IBMQ.save_account(qt) IBMQ.load_accounts() The error ...
1
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0answers
38 views

Clarification on the information content of a qubit [duplicate]

I saw a video in which a guy from IBM was explaining (very generally) quantum computing, it's difference with classical computing etc. The talk was not technical at all, it was intended for a broad ...
3
votes
1answer
121 views

How to put a quantum computer on the cloud?

What are the infrastructures needed to build a cloud quantum computing service like IBM Q Experience? It seems this is not a trivial task. IQX has been running for more than 3 years and yet it is ...
4
votes
1answer
102 views

Why are superconducting qubits the most popular approach to build a quantum computer?

There are many different physical implementations of qubits: NMR, spin qubit, N color center in diamond, superconducting qubit, trapped ions, photonics quantum computing, topological qubit, etc. ...
6
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0answers
50 views

Status of hidden shift and hidden subgroup problems

We know that solving a hidden subgroup problem over a non-commutative group is a long standing problem in quantum computing even for groups like $D_{2n}$ (alternatively can be written as $\mathbb{Z}_n ...
4
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2answers
77 views

Prove that the state $\sum_{S\in P_n}(-)^{\tau(S)}|S\rangle$ is invariant up to a phase when changing the basis

I am trying to prove that the $|S_{n}\rangle$ is $n$-lateral rotationally invariant, where $|S_{n}\rangle$ is defined as $$|S_{n}\rangle=\sum_{S \in P_{n}^{n}} (-)^{\tau(S)}|S\rangle\equiv\sum_{S \in ...
0
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1answer
47 views

Is this interpretation of quantum circuits right?

Just need some clarification: Results derived as the output of "running" a "quantum circuit" constructed from "quantum gates" are distributed in a certain way, based on the design, and the multiple ...

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