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Top Questions

3 votes
2 answers
2k views

What is the fastest quantum computational algorithm by which quantum computer speed up than classic one?

4 votes
2 answers
1k views

Is quantum teleportation fully secure (in principle)?

4 votes
2 answers
245 views

Necessity of decoding in fault-tolerant quantum computation

5 votes
2 answers
147 views

How to intuitively understand why $T$ gate can't be implemented transversally?

8 votes
2 answers
254 views

Non-entangling two-qubit gates

3 votes
1 answer
239 views

is cirq suitable for simulation of quantum error correction?

5 votes
2 answers
59 views

Reasonable Circuit Depth

3 votes
2 answers
166 views

Are continuous probability distributions over quantum channels possible?

4 votes
1 answer
101 views

How to represent a statevector in Dirac notation form using Qiskit?

2 votes
2 answers
272 views

Why is an X gate a quantum coin flip?

2 votes
2 answers
156 views

Matrix representation of SWAP on two qubit registers?

2 votes
2 answers
242 views

Is there any resource in which you can find some information about how much money is needed to start making any kind of qubit?

0 votes
2 answers
144 views

CNOT gate an elementary example of a single qubit quantum operation

2 votes
1 answer
125 views

What does the centered dot notation mean in the expression $|+\rangle|+\rangle\otimes(\cdot)$?

1 vote
1 answer
81 views

How can I represent the completely mixed state as $\frac I2=\frac14(\rho+X\rho X+Y\rho Y+Z\rho Z)$?

2 votes
1 answer
91 views

Why can any quantum channel be represented as a matrix?

1 vote
3 answers
68 views

Is the resolution of a physical qubit's probability limited?

5 votes
2 answers
52 views

What's the most efficient decomposition in terms of T-count of the 4-qubit Toffoli with 1 ancilla?

2 votes
1 answer
133 views

Heisenberg Uncertainty Principle (Nielsen and Chuang Box 2.4)

2 votes
1 answer
98 views

Fault-tolerant code and the error rate

2 votes
2 answers
92 views

Why are orthogonal quantum states represented as collinear in the Bloch sphere?

2 votes
1 answer
112 views

How to obtain the unitary operator to get specific partial trace?

1 vote
2 answers
84 views

get_statevector() not working with Qiskit Aer's statevector simulator

2 votes
4 answers
64 views

Inference on real hardware using a pre-trained quantum model on a simulator

3 votes
1 answer
105 views

HHL algorithm: how running the process $N$ times gives the vector components of the solution?

2 votes
2 answers
80 views

Preparing a superposition state modulo $k$

1 vote
1 answer
91 views

Confusion about quantum walks and the quantum walk operator

3 votes
1 answer
108 views

Show that $E_k=(I\otimes\langle e_k|)U(I\otimes|e_0\rangle)$ implies $U=\begin{bmatrix}[E_1]&\cdots\\ [E_2]&\cdots\\\vdots&\ddots\end{bmatrix}$

2 votes
1 answer
135 views

continuous time quantum walk on a cycle - transition matrix

4 votes
1 answer
80 views

Is the post-measurement state always pure after a partial measurement?

1 vote
1 answer
57 views

Speed versus number of qubits for RSA factorization

0 votes
1 answer
93 views

qiskit : how to measure multiple pauli strings

2 votes
1 answer
92 views

How can I see the circuit that was actually executed on the device in pennylane?

1 vote
1 answer
111 views

Show the linearity of $(\langle a_m|\otimes I_B\otimes I_C\otimes \langle d_q|) U(I_{A}\otimes I_B\otimes |0_{C}\rangle\otimes |0_{D}\rangle)$

1 vote
2 answers
66 views

Errors while encoding (3 qubit code)

2 votes
1 answer
66 views

Are relative phase Toffoli gates universal for reversible circuits?

1 vote
1 answer
83 views

How to rewrite the quantum state to qubits?

2 votes
1 answer
75 views

Is the assumption of constant per gate error probability $q$ in quantum computation proved , practical or valid?

1 vote
3 answers
45 views

What is the maximum number of qubits to execute a circuit on real hardware with IBM Quantum Experience and Qiskit?

3 votes
1 answer
57 views

How to simulate rectangular surface code with stim?

2 votes
2 answers
69 views

Quasiprobability decomposition of the CZ-gate

2 votes
1 answer
68 views

How to calculate the action of a channel on part of a quantum state?

0 votes
1 answer
85 views

How to implement this oracle?

2 votes
1 answer
66 views

Hilbert space vs RKHS

2 votes
1 answer
51 views

Truncating the bond dimension of an MPS -- how good is the approximation?

5 votes
1 answer
50 views

Action of a channel on an "unphysical" state

3 votes
1 answer
61 views

How do we compute quantum walks for a graph?

2 votes
1 answer
46 views

Solving a Bloch sphere where alpha is imaginary


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