Hottest Questions This Month

5

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2k

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What is the square root of the NOT gate?

quantum-gate matrix-representation

modified yesterday Community♦ 1

3

votes

2

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232

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Drawing the circuit in Qiskit - how to set same style as in Composer?

modified May 7 at 17:17 Durd3nT 402

4

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2

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308

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Quantum teleportation of a mixed state through a pure state?

density-matrix teleportation

answered May 4 at 21:39 Danylo Y 4,205

4

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2

answers

178

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Can I use Grover's algorithm for a function that has multiple arguments which satisfy it?

quantum-gate algorithm grovers-algorithm

modified Apr 28 at 18:29 Adam Zalcman 6,608

4

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3

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78

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How to find the distance between a given $\rho$ and the nearest pure state(s)?

quantum-state density-matrix fidelity trace-distance

answered May 7 at 10:03 Norbert Schuch 4,292

1

vote

2

answers

106

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Given 2 unknown qubits, which series of gates can put them in an equal superposition of $\vert 00 \rangle$ and $\vert 11 \rangle$?

quantum-gate

modified Apr 25 at 23:32 rjh324 1,247

2

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4

answers

126

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Can a qubit be entangled with an arbitrary quantum state, without altering it?

entanglement quantum-operation cryptography

modified May 6 at 16:13 DaftWullie 37.3k

3

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2

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205

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Is it possible to retrieve $|\psi_1\rangle,|\psi_2\rangle$ from their tensor product $|\psi_1\rangle\otimes|\psi_2\rangle$?

quantum-state entanglement tensor-product

modified Apr 27 at 9:46 glS 13.3k

4

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1

answer

205

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How could one implement a circuit using Grover's algorithm to solve a linear system of equations?

grovers-algorithm quantum-circuit simons-algorithm

modified May 8 at 10:17 Community♦ 1

5

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1

answer

137

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Does anyone know the list of all known universal sets of quantum gates?

quantum-gate universal-gates

modified Apr 24 at 6:14 Adam Zalcman 6,608

7

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1

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165

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What are examples of extremal non-projective POVMs?

measurement quantum-operation povm

modified May 5 at 11:12 glS 13.3k

4

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1

answer

173

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Bloch sphere visualization using Cirq, ProjectQ, PyQuil

programming cirq pyquil projectq

modified Apr 28 at 20:23 rjh324 1,247

2

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2

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148

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Making a Controlled-Z from a CNOT

quantum-gate circuit-construction

modified May 10 at 8:23 Durd3nT 402

4

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1

answer

136

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How do you build a circuit to make an equal superposition of $n$ outcomes?

algorithm circuit-construction entanglement

modified May 6 at 10:46 glS 13.3k

6

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1

answer

78

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Is the complexity of a quantum circuit constant in the depth of the circuit?

complexity-theory quantum-circuit

modified Apr 30 at 8:22 glS 13.3k

4

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3

answers

76

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What is the difference between Bloch's sphere and IBM's Q-sphere?

quantum-state ibm-q-experience bloch-sphere

answered Apr 23 at 22:28 Martin Vesely 8,462

5

votes

1

answer

116

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Does the circuit with qubit-wise CZ gates compute the inner product of two states? If not, is there another circuit that does?

qiskit quantum-state algorithm circuit-construction inner-product

modified Apr 25 at 19:05 Adam Zalcman 6,608

6

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1

answer

68

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List of problems that can be reduced to finding the ground state of a Hamiltonian

algorithm resource-request vqe

modified Apr 25 at 17:08 glS 13.3k

8

votes

1

answer

125

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Error in the Toth's 2012 paper: “Multipartite entanglement and high-precision metrology”?

entanglement entanglement-witness quantum-fisher-information quantum-metrology

answered Apr 25 at 11:10 Jonathan Trousdale 2,979

5

votes

1

answer

79

views

Can we calculate the quantum volume of a classical computer?

architecture technical-standards quantum-volume

modified 2 days ago glS 13.3k

6

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1

answer

78

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Does Grover's algorithm always give the correct answer with 100% certainty for two-qubit states?

qiskit grovers-algorithm

modified Apr 28 at 2:41 rjh324 1,247

2

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2

answers

98

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Estimating output amplitudes of quantum circuits as GapP functions

quantum-gate complexity-theory probability

answered Apr 17 at 14:12 tsgeorgios 1,246

7

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1

answer

204

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Why do I get this extra factor when working out the dynamics of an adiabatic quantum computation?

adiabatic-model

answered Apr 21 at 15:56 DaftWullie 37.3k

3

votes

1

answer

121

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What is the quantum Fourier transform of $\alpha|0\rangle+\beta|1\rangle$?

textbook-and-exercises quantum-fourier-transform

modified May 8 at 13:10 glS 13.3k

3

votes

1

answer

94

views

How to prove the fundamental equation in the theory of angular momentum $\sum_{l=x,y,z}\langle J_l^2\rangle\le\frac{N(N+2)}{4}$?

quantum-gate pauli-gates angular-momentum

modified Apr 19 at 13:25 glS 13.3k

5

votes

1

answer

72

views

What is the superop simulator in Qiskit for?

programming qiskit quantum-state simulation density-matrix

answered May 3 at 23:23 Egretta.Thula 659

3

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2

answers

115

views

Basic gates sets

quantum-gate universal-gates

answered Apr 18 at 6:29 Martin Vesely 8,462

4

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1

answer

87

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If $C$ is a Clifford circuit, is there necessarily a Clifford circuit $C'$ such that $CT=TC'$?

quantum-gate clifford-group

modified May 2 at 10:59 glS 13.3k

2

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3

answers

82

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What is the point of Grover's algorithm, really?

algorithm grovers-algorithm

answered May 13 at 0:51 benrg 294

0

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1

answer

62

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Does a CNOT quantum gate violate no cloning theorem? [duplicate]

quantum-gate physical-qubit superposition

answered May 1 at 15:48 KAJ226 8,206

3

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1

answer

161

views

What is the IQ plane?

quantum-state superconducting-quantum-computing tomography

modified May 2 at 10:50 glS 13.3k

5

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1

answer

76

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What algorithm does Qiskit use to decompose arbitrary n-qubit unitaries on Rotations + CNOT?

qiskit algorithm

modified Apr 26 at 7:35 rjh324 1,247

5

votes

1

answer

71

views

What is the difference between “Shot-Noise-Limit” and “Standard Quantum Limit”?

terminology quantum-fisher-information quantum-metrology

modified Apr 22 at 21:16 rjh324 1,247

2

votes

1

answer

98

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In the Bernstein-Vazirani circuit, if the secret is all 0s, would the oracle just be nothing?

algorithm bernstein-vazirani-algorithm

modified May 8 at 13:29 glS 13.3k

3

votes

1

answer

76

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Calculating the ground states of an Ising Hamiltonian on a real quantum computer

programming qiskit hamiltonian-simulation qaoa

modified Apr 22 at 16:22 glS 13.3k

4

votes

1

answer

123

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Integer Eigenvalues leading to periodicity

algorithm

modified May 11 at 16:07 Community♦ 1

1

vote

2

answers

74

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Is the tensor product of 2 Hadamard gates entangled?

entanglement textbook-and-exercises hadamard

modified Apr 23 at 8:58 Durd3nT 402

2

votes

1

answer

71

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Given $|\psi\rangle=(U_A\otimes U_B)|0,0\rangle$, is $|\psi\rangle\!\langle\psi|$ always a product state?

entanglement textbook-and-exercises density-matrix

modified Apr 22 at 12:59 glS 13.3k

1

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2

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113

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Intuitions about probabilities relating to evolving a two-qubit state through a CNOT gate

quantum-gate quantum-state probability

modified May 8 at 10:22 Community♦ 1

3

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1

answer

49

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Why are 3, rather than 2 gates used in quantum variational circuits?

quantum-gate measurement quantum-circuit quantum-enhanced-machine-learning

modified Apr 30 at 8:20 glS 13.3k

2

votes

2

answers

61

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Qiskit: count the type of gates on the qubit with the largest number of gates in a multi-qubit circuit

programming qiskit

modified Apr 29 at 21:45 KAJ226 8,206

0

votes

1

answer

99

views

Does $\mathrm{Tr}(\rho\sigma) > 0$ prove that a state $\sigma$ is separable?

entanglement density-matrix trace

modified Apr 21 at 14:11 Rammus 2,577

1

vote

1

answer

77

views

How to keep angles in degrees into quantum circuit using qiskit?

qiskit quantum-gate quantum-state

modified Apr 23 at 19:44 rjh324 1,247

3

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2

answers

46

views

Inverse of Statevector.from_label in Qiskit

programming qiskit

modified May 11 at 18:04 Frank 376

4

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1

answer

56

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Quantum computer speedups for classically efficient applications

physical-realization classical-computing applications

modified Apr 21 at 19:31 forky40 2,167

2

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1

answer

68

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Is RYY gate not available in IBM Quantum Composer?

quantum-gate ibm-q-experience circuit-construction

modified May 11 at 12:33 glS 13.3k

3

votes

1

answer

67

views

Why does applying a Hadamard gate three times to $|0\rangle$ result in a tiny imaginary component in the $|1\rangle$ amplitude?

programming qiskit ibm-q-experience python

modified Apr 29 at 20:37 Adam Zalcman 6,608

5

votes

2

answers

52

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Can any “control-something unitary” be written with control and target spaces flipped?

circuit-construction unitarity

modified May 12 at 14:23 glS 13.3k

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