36 How do I add 1+1 using a quantum computer? 2018-04-09T18:37:41.830

29 What is quantum gate teleportation? 2018-04-17T07:44:02.087

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

23 How can I implement an n-bit Toffoli gate? 2018-05-28T20:50:23.917

22 Why is it important to eliminate the garbage qubits? 2018-03-18T02:05:19.633

21 How to derive the CNOT matrix for a 3-qubit system where the control & target qubits are not adjacent? 2018-09-18T19:15:55.053

19 Explicit Conversion Between Universal Gate Sets 2018-08-31T10:02:20.183

18 How are quantum gates implemented in reality? 2018-03-23T11:12:37.637

18 How to interpret a quantum circuit as a matrix? 2018-06-11T13:08:53.187

18 Toffoli gate as FANOUT 2018-07-16T04:55:38.013

16 If quantum gates are reversible how can they possibly perform irreversible classical AND and OR operations? 2018-03-15T10:58:34.123

16 How are gates implemented in a continuous-variable quantum computer? 2018-03-30T23:12:48.783

15 Obtaining gate $e^{-i\Delta t Z}$ from elementary gates 2018-04-22T17:24:34.220

15 How do I build a gate from a matrix on Qiskit? 2018-12-16T17:13:17.150

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

14 Given a decomposition for a unitary $U$, how do you decompose the corresponding controlled unitary gate $C(U)$? 2018-03-26T15:37:09.230

14 Why do we use the standard gate set that we do? 2018-04-03T22:02:33.580

14 Do multi-qubit measurements make a difference in quantum circuits? 2018-04-04T10:49:17.640

14 Why are quantum gates unitary and not special unitary? 2018-05-12T21:57:48.573

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

13 How are quantum gates realised, in terms of the dynamic? 2018-03-22T11:54:59.120

13 What is the mathematical justification for the "universality" of the universal set of quantum gates (CNOT, H, Z, X and π/8)? 2018-03-23T19:56:19.330

13 What is the quantum circuit equivalent of a (delayed choice) quantum eraser? 2018-04-02T14:39:19.600

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 How to prove/disprove universality for a set of gates? 2018-06-30T01:00:47.627

13 Automatic compilation of quantum circuits 2018-08-24T18:05:02.970

12 How does Fourier sampling actually work (and solve the parity problem)? 2018-03-17T06:30:57.343

12 How to think about the Z gate in a Bloch sphere? 2018-06-01T20:54:15.730

12 Quantum XNOR Gate Construction 2018-06-14T01:59:39.580

12 How to construct a multi-qubit controlled-Z from elementary gates? 2018-08-23T22:34:21.137

12 State of the art gate speeds and decoherence times 2018-08-28T02:46:19.393

12 Approximating unitary matrices 2018-12-27T09:30:39.493

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

12 Is swap gate equivalent to just exchanging the wire of the two qubits? 2019-06-14T10:45:07.650

12 What is the opposite of measurement, in a quantum circuit? 2020-02-07T18:38:19.103

11 How can a controlled-Ry be made from CNOTs and rotations? 2018-05-25T10:42:39.130

11 Rotating about the y- or z-axis of the Bloch sphere 2018-06-04T09:13:08.030

11 Implementing "Classical AND Gate" and "Classical OR Gate" with a quantum circuit 2019-04-01T15:04:55.907

10 What happens if two separately entangled qubits are passed through a C-NOT gate? 2018-04-19T13:36:02.280

10 Implementation of the oracle of Grover's algorithm on IBM Q using three qubits 2018-05-31T22:35:40.077

10 How to implement the 4 Bell states on the IBM Q (composer)? 2018-06-07T15:03:24.000

10 Implementing a CCCNOT gate using only Toffoli gates 2018-06-19T17:44:46.100

10 How to implement a matrix exponential in a quantum circuit? 2018-06-27T12:32:54.373

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

10 How do you implement the Toffoli gate using only single-qubit and CNOT gates? 2018-08-05T17:41:03.960

10 How to construct matrix of regular and "flipped" 2-qubit CNOT? 2019-01-11T08:33:10.977

10 Understanding Google's “Quantum supremacy using a programmable superconducting processor” (Part 1): choice of gate set 2019-09-28T14:23:48.683

10 Simplification of "rotation swapping" circuit 2020-05-14T19:49:19.580

10 Superposition of quantum circuits 2020-10-15T20:14:06.550

9 How to implement the "Square root of Swap gate" on the IBM Q (composer)? 2018-06-04T06:48:49.567

9 Does conditional gate collapse controller's superposition? 2018-07-19T23:07:15.527

9 How to create quantum circuits from scratch 2019-07-22T13:17:36.957

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

9 Why are non-Clifford gates more complex than Clifford gates? 2020-01-31T11:11:01.810

9 Where is the parallelism in Deutsch-Jozsa algorithm? 2020-11-15T22:22:29.307

9 Is there a name for the 3-qubit gate that does NOT NOT NOTHING? 2020-12-27T20:10:26.567

8 New algorithm for faster QC simulation by IBM 2018-03-20T18:46:10.267

8 Does quantum control allow to implement any gate? 2018-03-31T18:19:41.093

8 How do you apply a CNOT on polarization qubits? 2018-04-17T08:15:49.980

8 Construct Controlled-$G^{\dagger}$ from known Controlled-$G$ 2018-06-26T07:34:08.697

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

8 Practical implementation of Hamiltonian Evolution 2018-07-20T12:05:30.820

8 Number of gates required to approximate arbitrary unitaries 2018-07-26T17:18:05.183

8 Possibility of a "reset" quantum gate 2018-07-31T12:05:29.067

8 How to say "apply CNOT on qubit 1 controlled by qubit 2"? 2018-09-26T19:09:05.833

8 Understanding the Group Leaders Optimization Algorithm 2018-10-17T17:25:00.750

8 How to prevent future loops using a control qubit? 2018-10-27T15:25:20.867

8 Is there any method of adding two operators in a circuit? 2019-01-30T13:21:55.213

8 Nielsen and Chuang's proof for 'approximating arbitrary unitary gates is generically hard' 2019-05-12T07:39:06.533

8 Could the Hadamard gate have been constructed differently with similar characteristics? 2019-10-13T01:15:06.540

8 How do I prove that the Hadamard satisfies $H\equiv e^{i\pi H/2}$? 2019-10-22T21:42:34.990

8 Why Google has used $\sqrt{X}$ and $\sqrt{Y}$ instead of $X$ and $Y$ in supremacy experiment? 2020-05-07T15:45:53.687

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

7 What is the difference between quantum control and quantum optimal control? 2018-03-30T11:45:20.377

7 How to avoid error when applying certain combinations of degree of freedom rotations using a quantum circuit? 2018-05-19T10:26:28.080

7 Why is the decomposition of a qubit-qutrit Hamiltonian in terms of Pauli and Gell-Mann matrices not unique? 2018-05-27T05:41:03.770

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

7 Quantum XOR Linked List Construction 2018-06-15T01:30:20.270

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

7 Expressing "Square root of Swap" gate in terms of CNOT 2018-06-26T01:54:44.063

7 The general form of unitary operations on a single qubit 2018-06-29T00:37:30.167

7 What are theta, phi and lambda in cu1(theta, ctl, tgt) and cu3(theta, phi, lam, ctl, tgt)? What are the rotation matrices being used? 2018-07-11T11:04:36.873

7 Matrix representation of continuous-variable gates 2018-07-12T21:15:06.683

7 SWAP gate(s) in the $R(\lambda^{-1})$ step of the HHL circuit for $4\times 4$ systems 2018-07-12T21:32:29.900

7 Is it possible to realize CNOT gate in 3 dimension? 2018-07-17T21:55:46.683

7 How do you represent the output of a quantum gate in terms of its basis vectors? 2018-07-29T00:53:45.717

7 Decomposition of arbitrary 2 qubit operator 2018-09-15T04:07:41.233

7 $R_z$ gate representations 2018-10-11T23:50:19.760

7 Simulation vs Construction of Fredkin gate with Toffoli gates 2018-10-15T12:37:37.033

7 What's an example of building a circuit $U_f$ that implements a simple function $f$? 2018-10-18T19:25:59.780

7 Is it better to use fewer gates or fewer working qubits? 2018-11-07T13:06:51.703

7 How to obtain Y rotation with only X and Z rotations gates? 2018-11-20T11:15:49.627

7 Composing the CNOT gate as a tensor product of two level matrices 2019-02-07T13:49:02.157

7 Show that these two expressions for the oracle transformation are equivalent 2019-02-16T13:06:27.943

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

7 Controlled Hadamard gate in ZX-calculus 2019-05-02T05:36:57.763

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

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