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5

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336

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Why is the transpose of a density matrix positive and trace preserving?

answered Feb 9 at 12:00 glS 12.2k

8

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2

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469

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How to check if a quantum circuit can be constructed for a given matrix representation?

mathematics matrix-representation unitarity quantum-circuit

modified Feb 8 at 21:56 ryanhill1 516

7

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3

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429

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What do the off-diagonal elements of a density matrix physically represent?

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modified Feb 2 at 18:19 Adam Zalcman 4,197

6

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2

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385

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How can one argue that the $S$-gate is Clifford while $T$-gate is not?

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modified 2 days ago glS 12.2k

7

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1

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406

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Does the no-hiding theorem suggest that quantum information is never destroyed?

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modified Jan 28 at 15:14 Nick ODell 173

5

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2

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306

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How to generalize the relationship HXH = Z for higher dimensions

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answered Jan 28 at 0:20 forky40 1,518

5

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4

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107

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Derivation of the identity $\sum_j p_j \langle \psi_j|M|\psi_j \rangle = \sum_j p_j \operatorname{tr}\left(|\psi_j \rangle \langle \psi_j|M\right)$

quantum-state mathematics measurement textbook-and-exercises

modified Jan 31 at 19:08 glS 12.2k

4

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3

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176

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Prove that $a|00\rangle+b|01\rangle+c|10\rangle+d|11\rangle$ is separable iff $ad-bc=0$

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modified Feb 3 at 21:15 Adam Zalcman 4,197

4

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2

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210

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If the eigenvalues of $Z$ are $\pm1$, why are the computational basis states labeled with “$0$” and “$1$”?

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modified Feb 2 at 10:37 glS 12.2k

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2

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279

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What's the default value for a quantum register?

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answered Feb 8 at 8:21 luciano 1,465

6

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1

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163

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What are tentpole topics in quantum computing?

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modified Feb 9 at 16:52 Mark S 4,273

4

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2

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113

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Computing expectation value of product of observables in PennyLane

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modified Jan 30 at 13:51 Josh Izaac 535

7

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2

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88

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Why does QAOA achieve quantum supremacy in an algorithmic sense?

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answered Feb 14 at 16:32 Mark S 4,273

4

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2

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118

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Partial trace and SWAP in the basis of subsystems

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modified Feb 11 at 2:04 Adam Zalcman 4,197

5

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80

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How can quantum interference happen in real world if a wave function does not have any physical meaning?

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answered Feb 7 at 14:39 glS 12.2k

1

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1

answer

149

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Take every second element of the array in Q#

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modified Feb 10 at 9:39 glS 12.2k

3

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2

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68

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Preparing Bell state $(1/\sqrt{2}) (|01\rangle + |10\rangle)$ in Qiskit

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modified Feb 5 at 17:08 glS 12.2k

1

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2

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109

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Was the Quantum Circuit Attribute “iden” renamed?

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modified Feb 10 at 16:54 glS 12.2k

4

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1

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133

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What is the difference between $|0\rangle+|1\rangle$ and a balanced mixture of $|0\rangle$ and $|1\rangle$? [duplicate]

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modified Feb 9 at 12:19 BrockenDuck 624

3

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1

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128

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How can we construct a control-control y-rotation (CCRy) gate in Qiskit?

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modified yesterday Faiyaz Hasan 107

5

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1

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161

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More efficient implementation of $4$-qubit gate

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answered Feb 17 at 8:46 DaftWullie 35.7k

2

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156

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+50

Condition that a tripartite/multipartite qubit state does/does not admit a Schmidt decomposition?

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answered Feb 23 at 8:21 Adam Zalcman 4,197

3

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3

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66

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How does one create the unitary sending $|0\rangle$ into a target quantum state?

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answered Feb 4 at 18:12 Rajiv Krishnakumar 381

3

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2

answers

65

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Is a projective measurements over a superposition of eigenstates possible?

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modified Feb 2 at 10:44 glS 12.2k

3

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1

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83

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How to limit the error probability in large scale quantum computers

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modified Feb 18 at 18:17 midor 199

1

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2

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63

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Q-Sphere representation of Bell States

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modified Feb 10 at 9:30 glS 12.2k

4

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59

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Is it possible to have access to real quantum computers that have more than 15 qubits for my master thesis?

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answered Jan 29 at 1:29 KAJ226 6,257

2

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2

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96

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Qiskit: Taking a QUBO matrix into `qubit_op'

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answered Feb 23 at 16:06 bubba 31

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58

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Find the unitary implementing the transformation $|0\rangle\to\frac1{\sqrt2}(|0\rangle+|1\rangle),|1\rangle\to\frac1{\sqrt2}(|0\rangle-|1\rangle)$ [closed]

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modified Feb 11 at 12:19 glS 12.2k

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3

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95

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What qiskit version?

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modified Jan 31 at 19:11 glS 12.2k

2

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3

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73

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error when running VQE in Qiskit

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modified Feb 2 at 10:44 glS 12.2k

4

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1

answer

117

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How to express a probability distribution $P(x,y,z)= \sum_\lambda P(x|y,\lambda)P(y|\lambda,z)P(z)P(\lambda)$ in terms of a trace of a density matrix?

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modified Feb 18 at 13:59 glS 12.2k

2

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4

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55

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In Bell's inequalities, what is the meaning of assuming that the physical properties $P_Q,P_R,P_S,P_T$ have definite values?

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answered Feb 10 at 14:59 glS 12.2k

4

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1

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66

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How to calculate the average fidelity of an amplitude damping channel

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modified Feb 17 at 18:33 Adam Zalcman 4,197

1

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1

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139

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Numpy DeprecationWarning flooding in IBM Quantum Lab

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modified Feb 5 at 11:26 luciano 1,465

3

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1

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102

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How to construct a controlled-Hadamard gate using single qubit gates and controlled phase-shift?

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modified Jan 31 at 19:10 glS 12.2k

2

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1

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161

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Can I 'shuffle' the qubits in my circuit?

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answered Feb 15 at 2:49 KAJ226 6,257

4

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1

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85

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SWAP Test as a Projective Measurement [closed]

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answered Feb 10 at 0:56 forky40 1,518

3

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1

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108

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Formal proof of Bell's inequality in CHSH form

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6

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2

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What is the computational complexity of quantum annealing?

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answered Feb 2 at 2:15 Dr. Prasanna Date 197

4

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2

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48

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Are the two ways of interpreting the expression $(|a\rangle\otimes|b\rangle)(\langle c|\otimes\langle d|)(|e\rangle\otimes |f\rangle)$ equivalent?

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answered Feb 8 at 23:28 chrysaor4 531

2

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1

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130

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Confusion about the output distribution of Haar random quantum states

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modified Feb 2 at 18:38 Adam Zalcman 4,197

3

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1

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101

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What are the differences between IBMQJobManager and Qiskit aqua QuantumInstance?

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modified Feb 16 at 9:05 glS 12.2k

7

votes

1

answer

61

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what matrix operations have better known time complexity on a quantum computer?

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modified Feb 6 at 20:49 Gokul Alex 807

2

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2

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78

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Qiskit order of multiplication and tensor product

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modified Feb 7 at 14:28 glS 12.2k

1

vote

1

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99

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Does sending a qubit using a quantum network through some conventional physical medium mean it is not with sender anymore after sending?

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modified Feb 22 at 23:27 Mariia Mykhailova 6,606

3

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1

answer

72

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In quantum teleportation, does Bob's qubit depend on Alice's $\alpha$ and $\beta$ coefficients?

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modified Feb 11 at 11:02 glS 12.2k

2

votes

1

answer

56

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How is the Grover iteration realized in an actual quantum circuit?

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modified Feb 18 at 10:52 glS 12.2k

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