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Question 1

0votes

0answers

51views

Understanding theorem 6 of postBQP=PP paper

In this paper, $\mathsf{BQP}_p$ is defined to be similar to $\mathsf{BQP}$ in all aspects except that the Born's measurement rule is changed. For a normalised state$$|{\psi}\rangle =\sum_x \alpha_x |...

Manish Kumar

953

askedNov 12 at 14:55

Question 2

0votes

1answer

53views

Quantum Phase Estimation

Implement the Quantum Phase Estimation (QPE) algorithm using the unitary operator S and the eigenstate∣1⟩ as the target qubit. Use 3 counting qubits and 1 target qubit.Assumptions / notation:Assume ...

Anitya Gupta

11

askedOct 30 at 11:00

Question 3

0votes

0answers

26views

How to choose the initial state of the reverse trajectory when applying fluctuation theorems and calculating entropy production?

In the literature on fluctuation theorems and stochastic entropy production, I often find different choices for the initial state of the reverse trajectory. This choice seems to depend on how the ...

Sayan Mondal

1

askedOct 25 at 3:35

Question 4

3votes

1answer

90views

Connection between observables and a quantum circuit

I am going through some lecture notes about Quantum Computing and I'm very confused about how an observable is related to a quantum state. I get that an observable contains the possible outcomes/...

Tony Chen

31

askedOct 14 at 1:05

Question 5

4votes

1answer

108views

Can an $n-1$ qubit entangled state be created from an $n$ qubit entangled state by LOCC?

Motivation: Creating residual entanglement from higher-order entanglement. Creating, for example, a two-qubit entangled state from a three-qubit entangled state.The Question: Let's say we have an $n$-...

mohadeseh azari

41

askedOct 11 at 15:46

Question 6

1vote

0answers

59views

Energy of one qubit in an interacting pair

Say I have two interacting qubits A, B with the following simple Hamiltonian:$$H = H_A \otimes \mathbb{I}_B + \mathbb{I}_A \otimes H_B + V_{AB}$$where $V_{AB}$ is any interaction term (for example ...

mmn_

11

askedSep 22 at 20:27

Question 7

1vote

1answer

55views

Constant Depth- Division by two quantum Circuit

Does designing a specific circuit for dividing a number of length n by two with a fixed depth of 9 count as an advancement in quantum computing?In practice and in real-world applications, which ...

mohammad zeynali Azim

11

askedSep 17 at 4:59

Question 8

0votes

1answer

94views

PGM (pretty good measurement) avg success probability upper bound

Is it true that $1/N \sum_i Tr[\pi_i \rho_i] \leq d /N$, given PGM projectors $\pi_i$, for $N$ equiprobable pure states with densities $\rho_i$ ,each in $d$ dimensions? I cannot find this referenced ...

qsfor

9

askedSep 4 at 16:37

Question 9

0votes

1answer

111views

Fannes–Audenaert Inequality with Relative Entropy

From Fannes–Audenaert Inequality, for two quantum states $\rho,\sigma\in\mathcal{D}(\mathcal{H})$ if $T=\frac{1}{2}\lVert\rho-\sigma\rVert_1$, where $\lVert.\rVert_1$ is the trace distance, we have\...

Nick Cooper

47

askedAug 20 at 1:11

Question 10

1vote

1answer

138views

Superadditivity of the trace distance for product states

Is $||\rho_{AB}-\sigma_A\otimes\sigma_B||_1\ge||\rho_A-\sigma_A||_1+||\rho_B-\sigma_B||_1$, where $||\cdot||_1$ is the trace distance, correct?I know that the quantum relative entropy has this ...

Nick Cooper

47

askedAug 19 at 23:54

Question 11

0votes

1answer

111views

Creating T gadgets

Consider an arbitrary Clifford circuit, terminating in a last layer of $T$ gates. Is it possible to construct a $T$ gadget using post selection in this setup?If we have $T$ gates in the beginning, ...

BlackHat18

1,629

askedJul 25 at 19:18

Question 12

2votes

1answer

123views

How to transform the density matrix from one basis to another basis

Suppose I have a density matrix for 2 qubits which is 4 by 4, in $Z$ basis $\left(|0\rangle,|1\rangle\right)$. Now I want to transform the density matrix to $X$ basis $\left(|+\rangle,|-\rangle\right)$...

sett the guy

95

askedJul 25 at 13:52

Question 13

0votes

0answers

98views

Question about tracing out one subsystem when two qubits are entangled

I encountered one question when preparing for the exam.(b) Suppose each of the qubits of the state $|\phi^+\rangle_{AB}$ undergoes a decoherence process of the form$$\rho \mapsto e^{-t} \rho + (1 - ...

sett the guy

95

askedJul 24 at 18:01

Question 14

3votes

2answers

371views

How would a DiVincenzo machine prepare the maximally mixed state with a small number of ancilla qubits?

For a while I had been thinking that the maximally mixed state is a problematic or pathological state not useful in quantum computing, insofar as it corresponds to a completely decohered state while ...

Mark Spinelli

16.3k

askedJul 22 at 15:17

Question 15

2votes

1answer

101views

Infinitesimal trace distance and metric

It is well known that the Bures distance between two infinitesimally close density matrices induces the Bures metric. Likewise the quantum Fisher information metric is related to the infinitesimal ...

nervxxx

612

askedJul 17 at 13:19

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Questions tagged [quantum-state]

Understanding theorem 6 of postBQP=PP paper

Quantum Phase Estimation

How to choose the initial state of the reverse trajectory when applying fluctuation theorems and calculating entropy production?

Connection between observables and a quantum circuit

Can an $n-1$ qubit entangled state be created from an $n$ qubit entangled state by LOCC?

Energy of one qubit in an interacting pair

Constant Depth- Division by two quantum Circuit

PGM (pretty good measurement) avg success probability upper bound

Fannes–Audenaert Inequality with Relative Entropy

Superadditivity of the trace distance for product states

Creating T gadgets

How to transform the density matrix from one basis to another basis

Question about tracing out one subsystem when two qubits are entangled

How would a DiVincenzo machine prepare the maximally mixed state with a small number of ancilla qubits?

Infinitesimal trace distance and metric

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