Hottest Questions This Month

2

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687

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Why do we have to measure the circuit before sending it to the real quantum computer?

answered Jul 22 at 6:16 Martin Vesely 9,245

1

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244

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Is Qiskit more popular than cirq? Why?

modified 15 hours ago user1271772 10.5k

1

vote

2

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478

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What happens to the Bell state qubits after the Quantum Teleporation?

entanglement teleportation bell-basis

modified Jul 19 at 10:25 DEX7RA 326

2

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2

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450

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Is it true that the way we must program Quantum Computers is through Total functions only, if so why?

programming algorithm

answered Jul 28 at 17:57 Martin Vesely 9,245

5

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2

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391

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What does it mean that 1 qubit can do the job of 1 ebit (entanglement bit)? (second Bennett's law)

notation terminology

modified Jul 21 at 18:56 DEX7RA 326

4

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3

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298

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How are eavesdroppers detected when using BB84 in the presence of noise?

quantum-operation noise fidelity bb84

answered Jul 14 at 11:48 sohamb172 77

4

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2

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141

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Inverting the depolarizing channel

quantum-operation linear-algebra depolarizing-channel shadow-tomography

modified yesterday Adam Zalcman 7,518

1

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5

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201

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How can I get the number of measurements where any specific qubit is equal to 0?

programming qiskit

answered Jul 5 at 21:11 LOC 181

4

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2

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254

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What are the conditions ensuring a two-qubit density matrix is positive semidefinite?

quantum-state mathematics density-matrix

modified Jul 20 at 15:20 glS♦ 14.3k

1

vote

3

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110

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Is every single-qubit unitary just a rotation around some unit vector on the Bloch sphere?

mathematics textbook-and-exercises resource-request bloch-sphere

answered Jul 7 at 21:14 glS♦ 14.3k

6

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2

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149

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Can one always find purifications which preserve equality of statistical mixtures?

quantum-state entanglement density-matrix partial-trace

answered Jul 26 at 20:21 Gv26 61

1

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1

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110

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Qiskit CNOT-gate matrix mixup?

qiskit quantum-gate entanglement pauli-gates

modified 20 hours ago Mujtaba Sattar Anonto 1

2

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2

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171

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How to understand combination states vs pure/mixed states?

quantum-state entanglement mathematics

answered Jul 18 at 17:06 Martin Vesely 9,245

6

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1

answer

132

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Why exactly are variational algorithms considered promising?

vqe qaoa quantum-advantage fault-tolerance

modified Jul 17 at 17:45 user1271772 10.5k

3

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3

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77

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How to derive $|0\rangle=\frac{1}{\sqrt{2}}(|+\rangle+|-\rangle)$?

quantum-state textbook-and-exercises superposition

modified 2 days ago glS♦ 14.3k

2

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3

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96

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What is the best way to extend a state $\rho_S$ to a tensor product of spaces ${\cal H}_S\otimes{\cal H}_A?$

quantum-state

answered Jul 23 at 17:03 Norbert Schuch 4,393

3

votes

1

answer

112

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Prove the fidelity can be written in terms of Pauli expectation values as ${\rm tr}(\rho\sigma)=\sum_k \chi_\rho(k)\chi_\sigma(\rho)$

quantum-state density-matrix pauli-gates fidelity

modified Jul 5 at 8:17 glS♦ 14.3k

2

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2

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86

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What are the constraints for the coefficents of the basis states in quantum computing?

quantum-state measurement textbook-and-exercises

modified Jul 26 at 1:24 glS♦ 14.3k

2

votes

1

answer

118

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What are min and max numbers of inputs needed to know whether the 4-bit classical Deutsch-Jozsa algorithm is balanced?

algorithm deutsch-jozsa-algorithm

modified Jul 18 at 18:17 glS♦ 14.3k

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1

answer

146

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Is there an algorithm that can decide if a state is a mixed state or a pure state?

quantum-state algorithm density-matrix

modified Jul 22 at 17:40 Learner 55

4

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2

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82

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Are all computational resources reducible to the time resource?

resource-request complexity-theory machine-learning

modified Jul 23 at 19:54 Greenstick 885

3

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2

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105

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Is it currently more cost effective/efficient to run a general purpose parallel algorithm on an accelerated quantum simulator or on CPUs?

performance quantum-parallelism

answered Jul 19 at 18:18 user1271772 10.5k

3

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1

answer

61

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How do you represent a Hadamard gate as a product of $R_x$ and $R_y$ gates?

quantum-gate circuit-construction textbook-and-exercises hadamard

modified Jul 9 at 15:27 glS♦ 14.3k

4

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1

answer

78

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What is the correlation between Toffoli and a more generic rotation shown in qiskit textbook

qiskit quantum-gate circuit-construction quantum-circuit

modified Jul 5 at 14:55 Tristan Nemoz 971

2

votes

3

answers

75

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How to describe the evolution of a density matrix using the Choi matrix?

qiskit quantum-operation density-matrix quantum-process-tomography

modified Jul 10 at 17:43 glS♦ 14.3k

2

votes

2

answers

90

views

Initial state for QAOA

optimization qaoa

answered Jul 27 at 10:28 Martin Vesely 9,245

2

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1

answer

69

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Initial state preparation for Hadamard test

quantum-circuit hadamard

modified Jul 27 at 11:06 Martin Vesely 9,245

2

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2

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68

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Are there problems that a classical computer can solve and a quantum computer can never solve?

classical-computing

modified Jul 18 at 18:20 glS♦ 14.3k

0

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1

answer

112

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Question about the Result Analysis of Ekera's Method in Short DLP

shors-algorithm

modified Jul 9 at 16:24 Martin Ekerå 31

0

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3

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85

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How does one interpret intuitively the CNOT gate?

quantum-gate entanglement

answered Jul 22 at 5:11 ljc 1

2

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2

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45

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How come classical Deutsch-Jozsa is $O(1)$ when allowing “a small error rate”?

textbook-and-exercises complexity-theory deutsch-jozsa-algorithm

modified 2 hours ago Tristan Nemoz 971

-2

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2

answers

73

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Tensor product and Dirac notation

mathematics tensor-product

answered Jul 23 at 11:23 Martin Vesely 9,245

1

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1

answer

106

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How to generate a quantum circuit from the quantum state $|1000\rangle+|0100\rangle+|0010\rangle+|0001\rangle$?

quantum-state circuit-construction textbook-and-exercises

answered Jul 26 at 16:45 prathamesh bhole 39

1

vote

1

answer

102

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Find the conditions under which the state $|\phi\rangle = \sum_{y=0}^{2^n -1} e^{\frac{2 \pi i a y}{2^n}} |y\rangle$ is unentangled

quantum-state entanglement textbook-and-exercises quantum-fourier-transform

modified Jul 5 at 23:46 Adam Zalcman 7,518

1

vote

1

answer

79

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How to normalise when the probability of measurement is zero?

quantum-state measurement textbook-and-exercises

modified Jul 23 at 12:21 Quantum Mechanic 1,059

1

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2

answers

60

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How to convert the output column vector or matrix into bra ket notation using python?

programming qiskit

modified Jul 9 at 12:56 Adrien Suau 4,050

2

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1

answer

58

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How is a classical bipartite state written in quantum notation?

quantum-state density-matrix notation

answered Jul 27 at 11:53 Rammus 3,367

2

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1

answer

74

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Prove that for a cq-state $\rho_{XE}$, $H_\infty(X|E) \ge H_\infty(X) - \log|E|$

entropy min-entropy conditional-min-entropy

modified Jul 6 at 19:45 QuestionEverything 1,518

0

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1

answer

55

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Get the inverse of a Hermitian operator for measurement in qiskit

programming qiskit measurement

modified Jul 7 at 21:21 glS♦ 14.3k

1

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2

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55

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Is ($|+⟩$$⟨0|$ + $|-⟩$$⟨1|$ ) similar to ($|0⟩$$⟨+|$ + $|1⟩$$⟨-|$ )?

mathematics textbook-and-exercises

answered Jul 22 at 23:52 KAJ226 9,466

1

vote

1

answer

53

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What is the “quantum phase” of a quantum state?

quantum-state notation

modified Jul 19 at 20:49 glS♦ 14.3k

3

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1

answer

87

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Bounding diamond norm distance using probability of error in transmission of classical information

quantum-operation classical-quantum channel-capacity diamond-norm

modified 12 hours ago Adam Zalcman 7,518

1

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1

answer

67

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Why is the quantum volume vastly greater than the number of qubits squared?

error-correction quantum-volume

modified Jul 26 at 1:25 glS♦ 14.3k

0

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2

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85

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How to assemble two quantum circuits whose qubit mapping states are different each other?

programming qiskit circuit-construction sabre qubit-mapping

answered Jul 6 at 13:27 KAJ226 9,466

0

votes

1

answer

82

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How to build and visualize circuit from matrix?

ibm-q-experience circuit-construction qasm quantum-computing-for-finance

modified Jul 4 at 20:50 Martin Vesely 9,245

1

vote

1

answer

80

views

How is eigendecomposition of a Hamiltonian equivalent to finding the minimum of an energy function?

d-wave annealing adiabatic-model

modified 15 hours ago user1271772 10.5k

1

vote

2

answers

78

views

How to build a QAOA Ansatz

programming qiskit qaoa

modified Jul 16 at 6:16 Nob som 1

2

votes

1

answer

47

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What is the complexity of loading $n$ inputs using a qRAM?

quantum-state algorithm

modified Jul 23 at 16:55 Craig Gidney 14.3k

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