24 How does measurement of one qubit affect the others? 2018-03-19T16:31:15.507

24 What is meant by the term "computational basis"? 2018-03-28T19:32:31.093

24 Quantum machine learning after Ewin Tang 2019-02-19T14:21:14.933

22 What's the difference between a pure and mixed quantum state? 2018-03-28T06:05:23.490

20 How can I build a circuit to generate an equal superposition of 3 outcomes for 2 qubits? 2018-06-12T09:48:37.680

20 What is the difference between a relative phase and a global phase? In particular, what is a phase? 2019-01-06T22:05:29.077

18 What is the difference between superpositions and mixed states? 2018-03-29T16:54:30.243

17 Alternative to Bloch sphere to represent a single qubit 2018-04-07T09:50:58.210

17 Significance of The Church of the Higher Hilbert space 2018-04-10T00:46:03.353

16 Quantum states are unit vectors... with respect to which norm? 2018-07-13T11:43:57.257

15 How to compactly represent multiple qubit states? 2018-03-17T14:03:05.840

15 Is it true to say that one qubit in an entangled state can instantaneously affect all others? 2018-05-11T14:47:33.197

15 No-cloning theorem and distinguishing between two non-orthogonal quantum states 2018-06-07T11:22:53.247

15 Why does the "Phase Kickback" mechanism work in the Quantum phase estimation algorithm? 2018-07-01T19:47:46.293

14 How do the probabilities of each state change after a transformation of a quantum gate? 2018-03-12T17:16:15.717

14 What makes quantum computations different from randomized classical computations? 2018-03-20T07:41:17.380

14 Representation of real numbers in quantum computers 2018-03-24T23:57:37.393

14 How to input 2 qubits in 2 Hadamard gates? 2018-06-08T12:29:33.077

14 Density matrices for pure states and mixed states 2018-06-14T18:55:38.513

13 How do you rotate a Fock state qubit? 2018-04-16T09:25:48.237

13 Is acting with a positive map on a state not part of a larger system allowed? 2018-05-15T07:33:05.183

13 Why are half angles used in the Bloch sphere representation of qubits? 2018-08-30T16:44:48.667

12 Embedding classical information into norm of a quantum state 2018-05-27T14:57:49.413

12 General construction of $W_n$-state 2018-10-05T09:18:25.400

12 How to calculate circuit depth properly? 2019-03-25T20:39:25.970

12 Does quantum computing already possess the level of abstraction to be explicable even without knowledge of physics? 2020-02-03T16:01:40.850

12 What are magic states? 2020-09-07T13:24:19.980

11 State produced by spontaneous parametric down-conversion (SPDC) 2018-03-13T00:50:59.097

11 Imperfect Quantum Copying 2018-10-24T13:43:48.723

10 What is the difference between a qubit and a quantum state? 2018-04-23T14:33:21.520

10 CNOT Gate on Entangled Qubits 2018-07-16T16:17:48.657

10 Sampling random circuits vs Solovay-Kitaev compiler 2019-06-29T14:13:53.470

9 What are the possible ways to visualise large, entangled states? 2018-07-06T14:31:41.693

9 How can I calculate the inner product of two quantum registers of different sizes? 2018-08-07T12:44:33.587

9 Why do we have to uncompute rather than simply set registers to zero? 2019-01-18T15:21:33.640

9 Optimal strategy to a quantum state game 2019-01-27T22:55:35.543

9 How and why does swap test works? 2019-10-17T19:02:55.577

8 How to check if a matrix is a valid density matrix? 2018-06-14T09:00:43.927

8 How to show that an n-level system is entangled? 2018-06-21T08:03:09.517

8 What are the P(0) and P(1) probabilities for the T transformation in quantum computing? 2018-06-28T18:20:31.200

8 What is intuition for the trace distance between quantum states? 2019-07-11T03:11:22.173

8 Do pure qudit states lie on a hypersphere in the Bloch representation? 2019-10-05T10:09:31.763

8 On the distribution of the fidelity of a random product state with an arbitrary many-qubit state 2019-11-17T13:59:24.003

7 Symmetry of tensor product w.r.t. Vazirani 2-qubit video 2018-03-25T01:02:30.473

7 Are there measuring standards (and units) for the identification of qubits? 2018-04-23T14:22:21.420

7 Does superdense coding allow to double the information capacity of a set of qubits? 2018-05-01T21:55:31.737

7 How to apply single and two qubit gates to 2 qubits multiple times? 2018-06-09T11:31:49.837

7 Measuring in standard basis meaning 2018-06-11T15:16:39.920

7 How to find a density matrix of a qubit? 2018-06-14T09:13:00.990

7 What does it mean for a density matrix to "act on a Hilbert space $\mathcal{H}"$? 2018-06-20T11:30:53.763

7 One-qubit gate results in QISKit 2018-06-24T21:23:36.790

7 What is the difference between $\vert 0 \rangle + \vert 1 \rangle$ and $\vert 0 \rangle \langle 0 \vert + \vert 1 \rangle \langle 1 \vert$? 2018-08-08T08:06:14.847

7 Transformation of a Bell state 2018-10-31T09:30:14.507

7 Why is the state of multiple qubits given by their tensor product? 2018-11-18T12:13:01.487

7 A two qubit state in a special form 2019-02-14T20:34:27.120

7 Most efficient way for general state generation 2019-05-26T19:45:49.610

7 How to interpret $-\rvert1\rangle \otimes \rvert1\rangle = -\rvert11\rangle$? 2019-05-30T09:33:54.660

7 Does the Choi-Jamiolkowski isomorphism really establish a connection between kinematics and dynamics? 2019-06-19T16:42:58.393

7 How is CNOT gate physically implemented in IBM Q? 2019-07-26T08:07:35.107

7 How can infinite information be theoretically encoded or stored in a single qubit? 2019-11-01T11:35:46.643

7 Does the trace distance have a geometrical interpretation? 2019-11-07T13:02:55.623

7 Why is the probability vector of a uniformly random state $\sum_i\alpha_i|i\rangle$ uniformly random only if $\alpha_i\in\mathbb C$? 2019-11-09T15:22:30.170

7 Preparing a quantum state from a classical probability distribution 2020-05-20T21:25:42.280

7 Why does a Hamiltonian have to be Hermitian? 2020-05-21T13:22:12.513

7 What makes representing qubits in a 3D real vector space possible? 2020-12-29T19:14:56.900

7 How to recover the normalization constant of the HHL solution 2020-12-30T01:36:56.127

7 Is there an efficient circuit implementing the unitary $U|x\rangle|0\rangle=|x\rangle\Big(\sqrt{1 - x/2^n}\,|0\rangle+\sqrt{x/2^n}|1\rangle\Big)?$ 2021-01-11T14:18:43.473

7 What do the off-diagonal elements of a density matrix physically represent? 2021-02-01T21:59:07.907

6 How does evolving a two-qubit state through a CNOT gate entangle them? 2018-03-21T10:14:14.440

6 How to compute the average value $\langle X_1 Z_2\rangle$ for a two-qubit system? 2018-04-10T18:24:33.557

6 Threshold and practical requirements for initial state preparation? 2018-05-01T06:51:41.983

6 How to calculate the state given by two qubits? 2018-06-08T10:15:20.497

6 How to check if 2 qubits are entangled? 2018-06-10T16:39:21.193

6 Are Absolutely Maximally Entangled states maximally entangled under all entanglement monotones? 2018-06-21T13:46:38.737

6 Use of change of phase gates 2018-06-24T08:49:03.517

6 How exactly is the stated composite state of the two registers being produced using the $R_{zz}$ controlled rotations? 2018-07-01T17:07:49.533

6 Stabilizer state verification and specification from state vector 2018-07-24T15:30:19.280

6 Solving linear systems represented by NxN matrices with N not power of 2 2018-07-27T09:09:01.500

6 Incorrectly Calculating Probability Amplitudes for 3-qbit Circuit 2018-08-03T15:06:12.370

6 What is the smallest quantum circuit to produce two-qubit state (a,b,b,b)? 2018-08-27T13:54:31.473

6 Symmetry in Conditional Phase Shift Gates and Realizing CNOT through HCZH 2018-09-05T04:00:30.973

6 How do we physically initialize qubits in a Quantum register? 2018-09-17T18:00:54.897

6 How to translate matrix back into Dirac notation? 2019-01-22T22:53:54.743

6 If $|\psi\rangle, U|\psi\rangle$ are known, how many pairs of such qubits are required to find the operator $U$? 2019-02-12T12:33:57.207

6 Summing states of two qubit registers 2019-03-25T17:08:33.790

6 Hidden shift problem as a benchmarking function 2019-04-04T04:36:47.230

6 Encoding bosonic degrees of freedom 2019-04-23T16:27:16.803

6 Quantum circuit for computing fidelity 2019-05-02T06:01:38.453

6 Question on state distinguishability 2019-06-07T23:06:22.833

6 $n$ qubit vs. a $d=2^n$ qudit states and measurements 2019-06-17T14:32:27.537

6 Non maximally entangled states for QKD 2019-08-10T10:02:45.103

6 What does W stand for in the W entangled state? 2019-10-20T18:40:50.500

6 Is a qubit always in superposition? 2019-12-27T05:17:26.323

6 How to prepare mixed states on a quantum computer? 2020-02-13T15:28:48.693

6 Why does full state reconstruction require at least $N+1$ MUBs? 2020-08-14T09:58:17.177

6 Can $|\Psi\rangle\simeq\sum_k |u_k\rangle|v_k\rangle$ be maximally entangled even if $\{|u_k\rangle\}_k,\{|v_k\rangle\}_k$ are not orthonormal? 2020-09-30T00:19:52.487

6 Quantum relative entropy with respect to a pure state 2020-10-14T17:32:58.323

6 Bob applies a projector - what happens to eigenvalues of Alice's reduced state? 2020-10-20T02:17:47.967

6 Superposition of quantum gates 2020-12-26T11:23:53.213