All Questions

The working of a quantum oracle is still not completely clear to me and I have a few questions: As I understand it, an oracle is a unitairy quantum gate and must somehow differentiate between the ...

Can you please help me to find an answer to this question: I am using qutip for the study of quantum systems. suppose I have calculated the solution of the master equation using the ...

I am using state vectors and operator matrices to test out my knowledge in a Python program. How would I represent the state $|+\rangle$ in Python? I want to then perform several operations in a ...

I am trying to write a simple circuit to understand the process of finding the set of parameters such that the cost function of that circuit in question is minimized. For that I understand one has to ...

In the HHL paper they make use of what they refer to as a controlled rotation in order to invert the eigenvalues of a Hermitian matrix $A$, which is what I am trying to understand. I understand the ...

For a controlled Z gate $CZ_{1,2,3}$ acting on 3 qubits, which of the following is correct? If it is the first one then what is the difference between that and a CZ gate acting on qubits 1 and 3? $$I ...

Natural 100% adding up what computers were invented for. Ourselves a processor, autonomously. Thru neural supremacy. Individual person with the right timing and thought process in his brain whom will ...

I was trying to see what IBM would do under the hood with a CCNOT gate. Something appears to be erroneous with the run. The circuit above should produce state 11100 with 100% probability, as ...

I'm trying to understand the three qubits bit-flip code. I use the book of Phillip Kaye An introduction to quantum computing. In this book he introduce the three qubits bit-flip code with this ...

This is a sequel to Motivation for the definition of k-distillability Geometrical interpretation from the definition of 1-distillability The eigenstate $|\psi\rangle$ of the partially ...

Definition of k-distillability For a bipartite state $\rho$, $H=H_A\otimes H_B$ and for an integer $k\geq 1$, $\rho$ is $k$-distillable if there exists a (non-normalized) state $|\psi\rangle\in ...

I am currently writing a script to automate the creation of parity curves for a 2 qubit bell state and then calculate fidelity and proving entanglement from that (inspired by this paper). It was going ...

Is there a known formula or a scaling behaviour for how many two-qubit gates are required to construct a general N-qubit unitary? I suppose there are several cases to consider: Exact representation ...

In the paper "Compiling basic linear algebra subroutines for quantum computers" here, they discuss (page 2 bottom right) using the HHL algorithm to multiply a vector by a matrix. However, after ...

As discussed in this question, the expected security of 1024-bit RSA is 80-bits: NIST SP 800-57 §5.6.1 p.62–64 specifies a correspondence between RSA modulus size $n$ and expected security strength ...

The pure states of a qudit inhabit the $\mathbb{CP}(d-1)$ manifold. Is it true that the pure states of $n$ qubits live on the $\mathbb{CP}(2^n-1)$ manifold? If the answer to the first question is yes,...

I'm going through some slides on the PPT/NPT criteria along with Horodecki's paper, and I'm kind of stuck. Let's take this slide: Firstly, why can we write a bipartite density matrix as $\sum_{...

In Chapter 6 of "Quantum Computation and Quantum Information" Textbook by Nielsen and Chuang, Box 6.1 gives a circuit example of Quantum Search Algorithm done on a two-bit sized search space. The ...

Does anyone know where I can find working Slack invite links to any of IBM's Slack pages? The Slack links on this support page are all broken. Thank you.

I have recently been studying quantum computing specially the cryptographic aspects of it. The books I followed is Nielsen and Chuang, and a book named Quantum Computing Explained by David McMohan. ...

I want to implement amplitude amplification using Q#. I have the operation $A$ that prepares my initial state and I need to compute $ A^{-1} $ to implement the algorithm. Is there an easy way to do ...

Based on the article given by J. L. Ball, I. Fuentes-Schuller, and F. P. Schuller, Phys. Lett. A 359, 550 (2006) had used the following expression of von-Neumann entropy \begin{equation} S = - \...

I have seen Why can the Discrete Fourier Transform be implemented efficiently as a quantum circuit?. This is not a duplicate. I am familiar with the decomposition of the QFT from Nielsen&Chuang ...

Let's say we got a CX with a Hadamard gate on the control gate and any state at the target gate, will the target necessarily become a superposition of two states? Best.

Problem definition I'm implementing a quantum circuit in qiskit for a Szegedy quantum walk, (reference, Fig 21.). It uses two registers of dimension $N$ ($N=3$) each one. The challenges I'm facing ...

I'm referring to an earlier question. It involves secret sharing based on the different measurement directions 3 people i.e Alice Bob and Charlie do. Now there is a block in the referred paper which ...

The Peres-Horodecki criteria for a 2*2 state states that if the smallest eigenvalue of the partial transpose of the state is negative, it is entangled, else it is separable. According to this paper (...

I have multiple different operators in matrix form and I need to find their common eigenstates. The challenge is that the common eigenstate is in a superposition of multiple states and isn't just a ...

I'm trying to implement the three qubit bit flip code in Qiskit. Therefore, I need to get the result of a measure of two ancilla qubits, to deduce which gate I need to use do recover my logical qubit....

Is swap gate equivalent to just exchanging the wire of the two qubits? if yes why not just switching the wire whenever we want to apply a swap gate?

Is there a way of eliminating a term of a superposition state? Let's say I have the state $$\frac{1}{\sqrt 2}|00\rangle + \frac{1}{2}|01\rangle + \frac{1}{2}|10\rangle$$ What operation would I do to ...

Since yesterday I'm trying to run on the new composer (quantum-computing.ibm.com) both new experiments (never run before) and older experiments (that have been successfully run and completed some ago) ...

How to apply the changes on circuit design for Grover's Algorithm n=5 in ibm q ? i Have tried n=3 which is already present there.

Quantum Entanglement and Geometry — Andreas Gabriel (2010) — Sec: 2.3.4 ~p. 11 Another basis for $d\times d$-dimensional matrices that has proven to be quite useful in quantum information theory is ...

This may be a fairly basic question, but in Nielsen & Chuang, the following circuit is given for simulating $\exp\left(-i\Delta t Z_1 \otimes Z_2 \otimes Z_3\right)$: which uses an ancilla qubit ...

I believe that there is some way to make a quantum computer by programming an FPGA with the D Flip-Flop. The D Flip Flop uses a square wave as the clock signal and another wave, the data input, that ...

I have a question while reading the quantum fidelity definition in Wikipedia Fidelity of quantum states, at the end of the Definition section of quantum fidelity formula, it says Explicit expression ...

I'm trying to program a controlled gate as the figure below in Qiskit. Should it be sufficient to separate and control individually the Hadamard gates?

Let $P$ be a projector and $Q = I-P$ be its complement. How to find probability $p$ and unitaries $U_1, U_2$ such that for any $\rho$, $P\rho P + Q\rho Q = p U_1\rho U_1^\dagger + (1-p)U_2\rho U_2^\...

I am getting confused as to how to perform gate operations using matrices and am hoping someone will help me walk through this example. Say I want to perform a Pauli-X gate on the 3rd qubit in a 3-...

I am wondering if there is a way to get advice\feedback here about the following: I am about to start a MS physics program. I am interested in quantum computing and my department has the option of ...

I am reading a paper on Quantum Secret Sharing Quantum Secret Sharing using GHZ states I have doubts regarding the initial phase of the paper, which are: Let me state what things I read and ...

On contrary to amplitude amplification, can I do some reflection such that my marked states' probability will vanish (ideally become zero but if there are small residuals also acceptable)? In order to ...

How does the act of erasing information increase the total entropy of the system? This goes by the name Landauer's principle. Some details are here. Can anyone shed more light on this?

I tried to run Grover's search for basis states with complex coefficients, including the marked basis (complex coefficients because the states are obtained from inverse QFT), but it could not amplify ...

I’m wondering that is there a way to separate phases of basis states from the magnitudes (namely putting phases on some new basis states with the same probability magnitude) if the exact values of ...

Is there anyone who reproduced the Bloch sphere given in the paper QuTiP: An open-source Python framework for the dynamics of open quantum systems by J. R. Johansson, P. D. Nation, Franco Nori? I am ...

I read "...an $n$ qubit array can represent $2^n$ possible array elements.." on this post. A classical $n$-bit array can represent $2^n$ possible array elements as well, so I'm confused about the ...

I am reading this paper entitled "Quantum algorithm for linear systems of equations" and am trying to understand a portion of the algorithm described on page 2 and in more detail in the appendix ...

I am writing a program where I need to find the eigenstates of an operator that is a Kronecker product of conditional quantum gates. I am wondering how I would compute this product in matrix form as ...