All Questions

I've been searching about quantum amplitude estimation techniques and read that it is customary to use an extra qubit to separate good and bad states using algorithm $A$ as $$ A|{0} \rangle^{\otimes^{...

Suppose I have a portfolio optimization problem where I have to minimize, $$qx^T\sum x - \mu^Tx$$ where q is the maximum risk and x is {0,1}^n and $\mu$ are the expected returns. Now I have to convert ...

Is there a method to correct an error of the form of $e^{ix}$, acted on a two qubit state without knowing the nature (the value of x) of the error? Also, can I rephrase the above question to: Is there ...

I was able to calculate the one and two-body integrals for the H2 with the following code ...

I am interested in solving a time dependent linear partial differential equation of the form $Ax=b$ which, in classical computing, would amount to looping over solutions of $Ax=b$ where $b$ is updated ...

In Qiskit, I need to define a custom gate or instruction that, once decomposed, turns into a series of basis gates, including measurements and classically controlled gates (this is the part that I can'...

I am designing an experiment which involves solving a linear system of equations of the form Ax=b. To do this, I am using the HHL algorithm on the IBMQ system. My ...

I was watching some lectures on qubits. They were talking about how to generate a Bell state. They described it as follows: Prepare state 00: $$\left |0 \right> \otimes \left |0 \right>$$ Apply ...

I read about Hadamard gate H and found it's matrix representation as follows: $$H_1=\frac{1}{\sqrt 2}\begin{pmatrix}1 & 1 \\1 & -1\end{pmatrix}$$ I wanted to know what will be the matrix ...

I prepared a quadratic optimization task with binary and integer variables and linear and quadratic constraints. I fed it into QuadraticProgram in Qiskit. After ...

This question is two-fold and considers general $n$-qubit operations on a quantum computer. First, can a general $n$-qubit operation be implemented on a quantum computer without the use of ancilla ...

From this link: Where equation 1 is: I can probably brute-force this by explicitly calculating this quantum circuit's effective 4x4 matrix and seeing that its equivalent to this teleportation ...

I am trying to implement the partial trace operation on IBMs quantum computer. I am simulating the depolarising channel with the following code ...

Can someone please help me making these gates on CIRQ programming: Decrement Gate (-1) Splitter Gate (If possible) I was having trouble implementing these and was not sure if it's possible either. ...

I am trying to build a large and quite complex three qubit quantum circuit on IBMs quantum computer. I have a specific unitary which I am trying to implement and I am building a circuit following the ...

I am running a very simple script just to learn how to use IBMQ, but my job will hang indefinitely and I am forced to terminate it. ...

I'm studying quantum error correction on Nielsen's Quantum Computation and Quantum Information, but I don't understand how it identifies the number of places where an error may occur, it uses ...

How can I put the unitary matrix $$e^\frac{i\pi}{2}I$$ to the quantum circuit? I don't know if it is belong to $$U3(\theta, \phi, \lambda), U2(\phi, \lambda), U1(\lambda)$$ Thanks a lot.

I'm currently able to get state vector in Qiskit using state_vector backend using something like : ...

I ran a 3-qubit measurement circuit on QASM simulator as well as on IBM Q Melbourne, Santiago and Vigo machines. The running time on the simulator is in few milliseconds (400-800) while in the case of ...

After having a discussion with a quantum computing colleague, a question came up: is there any meaningful measure of entanglement in a macroscopic (i.e. many body) system where you don't have the ...

Here is an exercise (4.27) from Nielsen and Chuang and I found the answer (given in the figure below) online without any explanation. The question was to construct a circuit by seeing a matrix (given ...

What is the importance of global phase? How it affect a unit vector if we see it on a Bloch sphere? What is the meaning of 'up to global phase' in exercise 4.3 of Nielsen and Chuang?

I'm struggling to find an analytic way to solve this problem. There are $4! = 24$ possible classical operations on the four 2-Cbit basis states. How many of these are achievable via the classical ...

What is the significance of different transpiling time, validating time, in queue time, running time for the same circuit run on different quantum systems for same no. of shots in IBM Q experience? ...

I'm reading this article which is explaining about quantum error correction and fault-tolerance. I'm wonder what "Definition 1" means. Especially, "There is C is an ((n, K)) (binary) ...

The two-qubit eigenvalue ($\lambda_i$ >= 0, $i=1,\ldots,4$, $\lambda_4=1-\lambda_1-\lambda_2-\lambda_3$) condition of Verstraete, Audenaert, de Bie and de Moor AbsoluteSeparability (p. 6) for ...

I am working with a very sparse matrix and it seems inefficient to load the full matrix as input into the Qiskit HHL algorithm. Is it possible to input only the non-zero elements, instead ? I am ...

I read some paper about Quantum Circuit Optimization but I am on a low level. And have some experience in ML. But what I don't understand is it possible that ML can help to optimize Quantum Circuits ...

On pg 376-377 of N&C, it gives 3 different diagrams showing how the various axis of the Bloch sphere will be contracted under the action of the channels, limiting the possible states after it's ...

I wanted to implement a non-unitary operation. I came to know that I can do it as a linear combination of unitaries from this paper (published version). Let us say I want to implement an operation ...

Let $E$ be the set of all correctable errors and $E_a, E_b \in E$. Let $\lbrace \vert c_1\rangle, \vert c_2\rangle, \ldots \vert c_k\rangle\rbrace$ be the basis of codewords in the codespace. It is ...

What would be measured if you measure two entangled qubits at exactly the same time?

I've been wondering, are there any known tasks/algorithms that can be performed on 1 quantum device, but also be somehow modified and split between several smaller devices? The thought behind the idea,...

Using Python how can I implement a quantum circuit that returns $|01\rangle$ or $|10\rangle$ using only $CX$, $RX$ and $RY$ gates, starting with random parametric gates as parameters and optimizing it ...

Let's say I have two arbitrary quantum states $|\psi\rangle$ and $|\phi\rangle$. I apply the SWAP test circuit (something like what is given here), and measure the first qubit to get either $0$ or $1$....

I've been learning about quantum computing, and I noticed that another way to describe the state vector is as a path in a binary tree where each level of tree represents another qubit, each node ...

The function $f:\{0,1\}^2\to\{0,1\}$ , $f(x_1x_0)=x_0$ returns the least significant bit of its argument. Solve the Simon's problem for this function and write down the number "a" (secret ...

When I run the following command qc.draw(output='mpl') for my circuit qc, I get this error: ...

would you kindly help me solve this problem: The function $f:\{0,1\}^2\to\{0,1\}$ , $f(x_1x_0)=x_0$ returns the least significant bit of its argument. What is the $U_f$ operator for this function?

I'm new to qiskit and I want to know how do I define a projector operator in qiskit? Specifically, I have prepared a 3 qubit system, and after applying a whole lot of gates and measuring it in a state ...

I have two circuits that I believe are equivalent. How can one check this on qiskit? Currently, I am executing both circuits and verifying that the counts are close (which they are) but I would like ...

It seems like I can use https://qiskit.org/documentation/stubs/qiskit.circuit.random.random_circuit.html but I would like to control the gates that are allowed. What is an efficient way to make random ...

Suppose Alice and Bob share the quantum state $\frac{1}{\sqrt 2}(|x\rangle + (-1)^b |y\rangle)$ for some $x\neq y \in \{0,1\}^2$ and $b \in \{0,1\}$. They both do not know $x,y$, and use some ...

We know for a pure state conversion $|\psi \rangle \rightarrow_\textrm{LOCC} |\phi \rangle$ via local operation and classical communication (LOCC), an entanglement monotone should not increase, that ...

When running pip show qiskit-ibmq-provider in the Anaconda Prompt I get the following: ...

what is the significance of varying the number of shots while running a circuit in a quantum machine and qasm simulator? Does more number of shots give better/accurate result? I am running a simple 2 ...

I am going through the QAOA section in the Qiskit Textbook - QAOA and am stuck in one of the steps. In section 5.2, the method for getting the Optimal Trial State Parameters are discussed. I do not ...

When I measure 2 and 3 qubits after putting H gate on all of them, there is a variation in probabilities of results in comparison with theoretical values (25% and 12.5%, respectively). This occurs on ...

According to the ManagedResults Documentation the class has a combine_results method, however when attempting to use it as follows: ...