26 If all quantum gates must be unitary, what about measurement? 2018-03-15T15:02:47.357

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

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

10 Proof of an Holevo information inequality 2018-05-25T17:48:26.070

9 Twirling Quantum Channels: Pauli and Clifford Twirling 2019-05-28T08:51:28.543

9 Does higher channel fidelity imply higher entanglement fidelity? 2019-12-20T16:28:54.260

8 What quantum channels are considered in quantum communication, and how does this choice affect the construction of error correction codes? 2018-05-22T10:14:21.380

8 Depolarizing channel implementation on IBM Q 2018-10-07T00:18:00.340

7 Advances in Quantum Channel Capacity 2018-06-29T08:09:05.213

7 How are Rigetti and IBM QX device parameters related to Kraus operators? 2018-11-05T21:52:22.943

7 How should we interpret these quantum logic gates as physical observables? 2019-04-26T01:28:55.697

7 Quantum channel representation of projective measurement 2019-06-13T00:57:22.930

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

7 Derive phase damping quantum operation 2019-07-27T14:21:40.190

7 Entanglement-assisted hashing bound for asymmetric depolarizing channels 2019-09-30T15:10:18.837

7 Positive semidefinite relationship after partial trace 2020-12-15T17:47:26.110

6 Is the Kraus representation of a quantum channel equivalent to a unitary evolution in an enlarged space? 2018-05-14T08:18:45.467

6 Can the Kraus decomposition always be chosen to be a statistical mixture of unitary evolutions? 2019-08-06T16:15:21.107

6 Is there a quantum operation whose output is always orthogonal to the input? 2019-10-03T08:19:37.670

6 Are perfectly LOCC-indistinguishable states necessarily identical? 2020-10-06T13:29:08.737

5 Deduce the Kraus operators of the dephasing channel using the Choi 2018-11-16T17:04:46.437

5 Confusion on the definition of the phase-damping channel 2018-11-26T11:40:24.430

5 How many Kraus operators are required to characterise a channel with different start and end dimensions? 2018-12-06T18:35:41.847

5 How does the vectorization map relate to the Choi and Kraus representations of a channel? 2019-03-29T17:19:23.093

5 What is Stinespring Dilation? 2019-03-30T21:55:02.887

5 What's the difference between Kraus operators and measurement operators? 2019-04-25T09:40:12.120

5 Quantum fidelity simplified formula while both of the density matrices are single qubit states 2019-06-13T16:11:03.647

5 Find the quantum operation corresponding to a given unitary evolution and projective measurement 2019-07-13T22:19:53.150

5 Do the eigenvalues of the Choi matrix have any direct physical interpretation? 2019-08-09T13:48:28.677

5 Why can any LOCC operation be written as $\sum_k (A_k\otimes B_k)\rho(A_k^\dagger\otimes B_k^\dagger)$? 2019-08-12T13:07:38.687

5 Explicit form for composition of Choi representation quantum channels 2020-03-08T21:30:50.937

5 What does it mean to take the Choi-Jamiolkowski of a quantum channel? 2020-04-16T22:29:17.530

5 When can a non-completely-positive evolution of a state be physical? 2020-05-02T22:14:42.217

5 What does the adjoint of a channel represent physically? 2020-07-15T23:29:21.843

5 Stinespring dilation: Size of environment 2020-12-10T19:20:42.570

5 Unknown quantum circuit symbol 2020-12-15T04:31:12.000

4 What is the difference between signaling and non-signaling quantum correlations, and what is a signaling channel? 2018-03-30T14:29:03.303

4 Image of a sum of positive operators contains the images of each individual operator? 2018-09-05T01:07:22.730

4 Quantum channel Holevo information additivity: proof approach 2018-11-20T10:28:44.077

4 How to find the operator sum representation of the depolarizing channel? 2018-12-16T20:35:45.460

4 Real-life examples of classical-quantum channels 2019-01-22T16:25:48.343

4 For 2x2 and 2x3 systems, is the partial transpose the only positive but not CP operation? 2019-02-18T13:15:38.507

4 POVM three-qubit circuit for symmetric quantum states 2019-03-04T15:09:16.007

4 Understanding classical vs. quantum channel capacities 2019-04-02T09:00:43.407

4 Implementing a depolarizing channel for 2 qubits on IBM Q 2019-04-29T08:49:20.973

4 Degradable channels and their quantum capacity 2019-05-09T15:39:08.343

4 How are witness operators physically implemented? 2019-05-14T07:35:55.500

4 Structural Physical Approximation of Partial Transpose 2019-05-21T09:45:51.753

4 What is the unitary operator realizing a given CPTP operator 2019-07-31T22:59:33.860

4 Do the Kraus operators of a CPTP channel need to be orthogonal? 2019-08-08T12:00:34.083

4 What goes wrong if I try to simulate a system with a larger Hilbert space with a smaller Hilbert space? 2019-11-14T06:46:24.370

4 What is the difference between intercept-resend attack and measure-resend attack? 2019-11-25T06:05:15.473

4 How is the partial trace related to the operator sum representation? 2019-11-25T13:25:14.487

4 How to obtain the tensor-product of two quantum operations (superoperators) explicitly? 2019-12-04T04:01:38.077

4 Mutual information of Choi state=0, what would that imply about the quantum channel? 2020-06-18T13:31:47.693

4 Can local projections increase entanglement? 2020-09-20T17:28:45.983

4 Alternative definition of the coherent information of a quantum channel 2020-10-27T12:25:23.427

4 How to perform this $d$-dimensional unitary operation on IBM Q? 2020-10-29T03:29:29.513

4 Unitary over bipartite states that can turn a non-product state into a product state 2020-12-19T20:14:30.060

4 How can I fit an unknown quantum channel? 2021-01-18T16:59:45.550

4 Is un-computing $U$ a good proxy for circuit fidelity? 2021-01-23T00:35:08.757

4 What is the general form of a classical-quantum state? 2021-02-15T09:44:54.193

4 How to calculate the average fidelity of an amplitude damping channel 2021-02-16T17:28:47.417

3 Tensor product properties used to obtain Kraus operator decomposition of a channel 2018-06-01T20:40:29.040

3 Isometric Extension of an Erasure Channel 2018-11-26T22:23:24.493

3 Dephasing channels 2018-12-04T15:32:39.533

3 What do you specify when you physically apply a unitary? 2019-01-13T12:50:38.063

3 The meaning of measurements in different bases 2019-03-01T17:52:01.140

3 Estimating the depolarizing probability of depolarizing channels 2019-03-11T14:54:43.750

3 Clarifying the relationship of the probabilities of depolarizing channel and relaxation/dephasing times 2019-03-20T12:28:57.173

3 Quantum Fisher information 2019-04-01T14:19:29.937

3 Counting channel uses of the lossy bosonic channel or definition of channel uses 2019-05-08T09:50:26.760

3 Quantum channel cannot increase Holevo information of an ensemble 2019-05-09T09:58:49.123

3 State of a system after the second qubit of a Bell state sent through a bit flip error channel 2019-05-13T20:29:00.273

3 How does a map being "only" positive reflect on its Choi representation? 2019-05-14T17:59:22.707

3 Holevo quantity and mutual information 2019-08-07T17:54:47.043

3 Why does entanglement not increase the classical capacity of a channel? 2019-09-10T18:50:43.770

3 If a state is only "close to" an eigenstate of an operator, how many applications of the operator does it take to scramble the state? 2019-10-29T21:28:06.870

3 How to define a quantum channel for the partial trace? 2019-11-15T10:32:58.230

3 Simulating Classical Probabilistic Transitions with superoperators 2019-12-09T02:28:14.853

3 Proof that quantum entanglement does not increase the asymptotic capacity of classical channel 2019-12-09T13:30:13.680

3 Optimizing over quantum channels 2020-01-16T11:31:47.577

3 What does it mean "less than identity" in the operator sum representation? 2020-01-18T16:02:12.077

3 Forbidden/allowed outputs of a quantum channel 2020-01-27T19:10:10.347

3 Confusing notation in Wikipedia's quantum channel article 2020-03-18T13:19:25.713

3 $M(\rho)=\operatorname{Tr}_2\left(\ U\ \rho\otimes\rho_2\ U^{\dagger}\right)$is unitary $\iff\ U=U_1\otimes U_2$, a product of $2$ unitary operators? 2020-05-03T16:14:37.353

3 How to compute the tensor product of the depolarizing channel with the identity? 2020-05-19T10:20:11.083

3 Representing a von Neumann measurement as $[\mathcal{I} \otimes P_i] U(\rho_s \otimes \rho_a)U^{-1} [\mathcal{I} \otimes P_i]$, how do we choose $U$? 2020-07-15T14:43:17.730

3 Why do quantum operations need to be reversible? 2020-07-22T11:44:55.923

3 How to find the unitary operation of a depolarizing channel? 2020-09-01T16:18:02.667

3 Equivalence of two ways to recover a map from its Choi state 2020-09-03T15:19:02.403

3 Why do the constant operations in a quantum computer need second qubits? 2020-10-27T20:21:27.947

3 Is there some notion of work associated with performing a measurement? 2021-02-18T01:37:21.903

2 Three sender quantum simultaneous decoder conjecture 2018-11-20T10:01:02.377

2 What is a complementary map? 2019-03-28T08:49:48.863

2 What is the relevance of preservation of trace in completely postive trace preserving (CPTP) maps? 2019-05-08T07:02:54.823

2 Direct derivation of the Kraus representation from the natural representation, using SVD 2019-05-14T08:15:52.907

2 Does the dilation in Naimark's theorem produce a state? 2019-05-17T18:53:17.017

2 Are CPTP operators and unitary operators the same thing? 2019-07-31T15:59:14.833