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

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

13 How does approximating gates via universal gates scale with the length of the computation? 2018-03-19T23:00:47.297

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

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

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

10 Shortest sequence of universal quantum gates that correspond to a given unitary 2018-05-13T14:09:15.530

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

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

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

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

9 How can I see, without math, the action of a gate in matrix form? 2020-03-01T23:16:33.900

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

8 Basic approximation in Solovay-Kitaev algorithm 2018-07-05T10:27:56.043

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

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

8 How is it possible to implement unitary operator when its size is exponential in inputs? 2019-04-23T01:06:17.220

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

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

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

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

7 Minimum number of CNOTs for Toffoli with non-adjacent controls 2018-08-07T05:35:22.910

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

7 Is there a general method to implement a 'greater than' quantum circuit? 2018-10-05T11:03:34.360

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

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 Would IBM's "compiler" turn my identity circuit into nothing? 2020-08-17T03:10:07.640

6 Quantum Ripple Carry Adder Construction 2018-06-14T18:17:04.917

6 Arbitrary powers of NOT and SWAP 2018-07-18T08:13:17.877

6 Decomposition of an arbitrary 1-qubit gate into a specific gateset 2018-09-18T08:30:32.567

6 Clarification needed: "Simulation" of $e^{-iHt}$ and its time complexity 2018-11-04T10:21:58.303

6 Hadamard gate as a product of $R_x$, $R_z$ and a phase 2019-01-24T12:22:28.243

6 How to decompose a controlled unitary $C(U)$ operation where $U$ is a 2-qubit gate? 2019-06-03T18:01:33.740

6 How to factor Ising YY coupling gate into product of basic gates? 2019-10-27T09:30:13.167

6 Decomposing gates resembling exponentiated members of desired gateset 2020-12-04T19:11:50.827

5 What components are needed to realize a photonic CNOT gate? 2018-06-27T03:13:05.430

5 How do we code the matrix for a controlled operation knowing the control qubit, the target qubit and the $2\times 2$ unitary? 2018-08-04T11:05:54.010

5 How can I decompose a gate into $\{\mathrm{CNOT}, \mathrm{H}, \mathrm{P}(\theta)\}$? 2018-09-30T13:08:49.243

5 Measuring the Hamiltonian in the VQE 2018-11-17T16:34:49.463

5 Construction of ${R_n(\theta)}$ using only the Hadamard and ${\pi/8}$ gates 2018-12-04T15:26:31.950

5 Decomposition of any 2-level matrix into single qubit and CNOT gates 2019-02-08T12:39:52.433

5 Implement Fredkin gate with square root of swap 2019-03-13T21:14:40.327

5 Transform matrix into a combination of simple quantum gates 2019-05-22T01:11:14.637

5 How can I fill a unitary knowing only its first column? 2020-03-20T05:38:59.657

5 Equivalence checking of quantum circuits up to error 2020-07-16T08:08:39.267

5 Reducing the depth of quantum circuits with ancilla qubits 2020-09-17T10:54:16.190

5 How to create the state $\vert 0 \rangle+i \vert 1 \rangle$ using elementary gates? 2021-01-18T16:15:06.850

5 More efficient implementation of $4$-qubit gate 2021-02-10T21:27:31.430

4 Square root of NOT as a time-dependent unitary matrix 2018-07-04T17:35:08.130

4 Rewrite circuit with measurements with unitaries 2019-03-06T13:43:06.730

4 How to construct a circuit to perform this operation? Is there a general way of getting a circuit from a matrix? 2019-11-25T17:19:38.903

4 How to find a circuit for the roots of QFT? 2020-06-20T04:08:56.750

4 How can you decompose Grover's diffusion operator into gates? 2020-08-14T09:41:32.357

4 Adding a phase to qubit: why is it necessary for arbitrary single qubit gate 2020-08-20T17:41:45.820

4 CNOT expressed with CZ and H gates by taking into account HZH =X 2020-09-17T06:52:49.807

3 Doing maths with controlled-half NOTs 2018-07-16T05:23:44.857

3 Circuit to construct a $n$-qubit state which is a superposition of states with only a single qubit being $\lvert1\rangle$ 2018-11-02T13:30:39.323

3 Implementing gate with two parameters using Qiskit in Python 2018-11-26T12:57:30.207

3 Implementing these $N×N$ matrices on $\log N$ qubits 2019-03-29T12:44:46.467

3 Making a maximally mixed 2-qubit state in the IBM Q 2019-04-29T23:21:54.677

3 Minimal quantum OR circuit 2019-05-08T20:18:30.940

3 How to create an $n$-qubit normally controlled gate? 2019-06-26T16:18:00.343

3 Calculate the square root of Euler angles 2019-06-27T17:22:23.247

3 control gate with 3 inputs, two control and rotation gate 2019-07-07T20:40:58.733

3 Cost of controlled-$U_i$ 2020-03-14T23:00:06.327

3 Implementing a controlled-controlled-U using controlled-U 2020-04-18T17:27:16.853

3 What is the complexity of splitting a state into a superposition of $n$ computational basis states? 2020-04-28T21:49:29.157

3 Are Toffoli gates actually used in designing quantum circuits? 2020-05-08T13:49:35.907

3 Decomposition of $|110\rangle \leftrightarrow |000\rangle$ Exchange Gate 2020-09-08T07:44:00.143

3 Gate-level implementation of Eigenvalue-Inversion in HHL 2020-12-27T18:45:51.953

2 What quantum gate is XNOR equivalent to? 2018-10-01T01:00:52.683

2 How to construct a quantum gate producing 1 if r divides x, 0 otherwise? 2018-10-20T19:17:55.793

2 Gate sequence for exponential of product of Pauli Z operators 2019-01-09T21:50:06.197

2 How to implement a $\frac{\theta}{2}$ rotation from $\theta$ rotation? 2019-02-10T15:44:59.577

2 Decompose a general two-qubit gate into general controlled-qubit gates 2019-02-13T22:21:12.827

2 If CNOTs and single qubit gates are universal then why do we need to prove that controlled U operations can be composed by them as well? 2019-02-17T16:10:22.100

2 Building an N-qubit Controlled S Gate 2019-02-27T07:02:28.707

2 Optimise implementation of a quantum algorithm when an input is fixed 2019-03-05T13:11:52.627

2 Using Quantum Fourier Transform in adding two 2-bit numbers 2019-06-26T15:06:23.697

2 Decomposing a controlled phase gate into CNOTs 2019-10-23T20:48:02.857

2 How to prove that a matrix is an arbitrary unitary? 2020-03-19T10:20:12.647

2 Decompose Toffoli gate with minimum cost for IBM quantum computer 2020-03-27T23:49:45.187

2 What are the differences between the Toffoli and Fredkin gates (historical, practical, etc.) 2020-05-06T15:44:10.373

2 How to define Q-operator in Quantum Amplitude Estimation 2020-08-31T15:20:41.293

2 Representation of multiple qubit matrices in Dirac notation 2021-01-22T08:51:02.060

2 How does MCPhaseGate/MCU1Gate works internally in qiskit? 2021-02-21T04:39:16.577

2 How to implement $\sqrt{iSWAP}$ in Qiskit 2021-02-22T00:35:11.793

1 How does the stated Pauli decomposition for $\operatorname{CP\cdot A\cdot CP}$ arise? 2018-10-19T11:41:26.370

1 Creating a time dependent custom gate in Quirk 2019-01-20T13:21:52.203