Questions tagged [cirq]

A python framework for creating, editing, and invoking Noisy Intermediate Scale Quantum (NISQ) circuits. It is a Python library for writing, manipulating, and optimizing quantum circuits and running them against quantum computers and simulators.

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Why `cirq` needs `Qid` class instead of just `Qudit` class?

I am just wondering in what way cirq.Qid class generalizes qudits. From cirq.Qid documentation we read that it Identifies a ...
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2answers
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How do you represent one-qubit rotations in two registers as a $4\times 4$ unitary matrix?

Let's say you have a circuit that performs a Z-rotation in the first register, and a Y-rotation in second register. How can we express this "moment" in terms of a 4x4 matrix, i.e. a two-...
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Bloch sphere visualization using Cirq, ProjectQ, PyQuil

Is there a way to visualize the Bloch sphere using Cirq, ProjectQ, and/or PyQuil, as it is possible using plot_bloch_vector in Qiskit?
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Adding Quantum State Tomography Step to HHL Algorithm (Cirq)

Over the past month, I have been learning about the HHL algorithm and am interested in extending the Cirq implementation to include the quantum state tomography step to extract the amplitudes or ...
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How to implement NM Algorithm for Variational Quantum Eigensolver?

First of all: thanks for reading again. I appreciate the feedback I have gotten from this community the past weeks as I started to feel ready to ask questions about quantum computing topics. I am ...
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How to avoid Cirq: State_vector is not normalized error for Feedback-loop in optimizer?

I am doing a VQE in Cirq, but sometimes I get this error while running steps of the classical optimization loop: State_vector is not normalized instead had norm 1.0000000010132789 And therefore the ...
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1answer
64 views

Expectation value of an arbitrary observable. My own definition and `cirq` limitations

In my previous question I was struggling with the definition of expectation value of an observable for a circuit. Here is what I have derived after some support (I simplify the definition to 2-qubit ...
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1answer
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How can I compose the Ising XXPOW,YYPOW and ZZPOW gate in single qubit gates and CNOT,…?

I am a bit stuck in decomposing these gates in single qubit gates, in the Cirq documentation it is written, for example that XX is for example the tensor product of Rx gates. But when I calculate ...
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Multiplying quantum circuits in cirq using * and computing “expectation values”

I am reading cirq guide about Simulation and there is an example in "Expectation values" paragraph that I don't understand. Everything boils down to the following snippet: ...
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1answer
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How to use pass_operation_over with cirq.Operation? [closed]

Lately I saw a pull request in the Cirq GiHub repo where some dev said a test should be defined, with these constraints: You need to find a case where a ...
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1answer
35 views

Setting the Initial State of Density Matrix Simulation in Cirq

I am trying to use the DensityMatrixSimulator in Cirq. I want to append gates to the circuit conditional on measurements. In order to reduce computational resources, I am trying to run these ...
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How to create an observable: 'Identity \tensor Pauli gate' in Cirq

I am working on an implementation of the RQAOA algorithm on the Maxcut problem in Cirq. My graph G has n vertices. And after running a QAOA circuit with n qubits I obtain a state gammabeta (a vertical ...
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In Cirq, how do you display circuit diagrams that are “prettier” than the ones displayed by default?

This is a duplicate of a question that was asked on the Cirq issues page. I'm duplicating this question to increase it's visibility. The standard way to print circuits in Cirq is by calling ...
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Best way to compute $\langle a|B|a \rangle$ in Cirq, where a is a state obtained running circuit A. And B is a different Quantum Circuit

I am implementing RQAOA in Cirq. After running regular QAOA to find an optimal state a (This I have done successfully). I need to calculate $\langle a|Z_iZ_j|a\...
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Why wont my custom controlled gates in Cirq work on a simulator?

To initialize a state in Cirq, I created a custom controlled rotation and a custom rotation gate. The effect of applying the custom controlled gates to the qubits doesn't seem to affect the state. ...
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1answer
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Is there a way to present conjugate transpose of a Y Pauli rotation as a Cirq Operator?

Given: Ry(theta) acting on one qubit I'm trying to use existing Cirq Operators to build the conjugate transpose of the above gate. I need the operator to produce the exact unitary of the given gate ...
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Random Circuit Generation in Cirq

I am trying to improve an optimization method as describe in this paper: enter link description here For that I need to create many random equivalent circuits. In my experiment I have 6 beam splitters ...
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209 views

Can I run Cirq on IBMQ?

Google's quantum computer is not yet available for the public. Is it possible to run Cirq on IBM's quantum computers, instead of Qiskit? And if so, how can I do it? Thank you!
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What are the libararies for Machine Learning on NISQ Chip? And What are the roadmaps?

Nowadays quantum learning is hiring. And we can see mainly two different area. One of them is variational algorithms part. And the other one is classical learning for quantum systems like NISQ. (Some ...
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1answer
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What is a good program to practice using a quantum algorithm? Should I use Cirq or Qiskit?

I am starting to learn about Quantum Computers and Quantum Algorithms. I also started reading about Qiskit and Cirq. I really like learning about them and hopefully I can be a Software Engineer with ...
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Interpret graph nodes as qubits

I am trying implement MAXCUT using QAOA. I have a graph with edges defined by an edges set. My edges set looks a bit like this: ...
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1answer
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Cirq: n-qubit GHZ state

I am trying to write $n$ party GHZ state but at the end of the day, it seems like bi partite state. I am missing a detail. Here is my code ...
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375 views

VQE Cirq example

Is my understanding correct that in this example the Hamiltonian measurement is not performed through measuring individual Pauli operators because all its terms are mutually commuting? So, for each ...
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1answer
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Cirq: Result of rotating qubit measurements never come [0 1] or [1 0 ], always come as [0,0] or [1,1]

I am creating a 2 qubit entangled state: ...
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1answer
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In Simon's algorithm, is there a general method to define an oracle given a certain periodicity?

I have to implement Simon's algorithm in Cirq. I have problems determining the oracle $f(x)$ defined such that $f(x)=f(x\oplus a)$ from a certain value of $a$. Given a random $a$, is there a general ...
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Implementing Cirq Coding Gates

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. ...
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Cirq.simulate expectation value of a Hamiltonian

I want to simulate the final state of an ansatz in cirq using simulate. Now I want to calculate the expectation value of a Hamiltonian. How do I do this? I can only find simulator.run examples in cirq....
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Access and set_state during quantum computation simulation in cirq

The documentation for Cirq mentions the possibility to step through a circuit's moments, and access the exact wavefunction via step.state_vector(), and edit set it ...
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1answer
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Does Cirq support GPU acceleration?

I'm wondering if Cirq does (or plans to) support GPU acceleration of matrix operations, including density matrix simulations. I would like to speed up training and evaluations of variational circuits ...
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2answers
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Why is the Measurement Result Always 1? (expected to find uniformly random measurement)

I created a $|0\rangle$ state then applied $H$ gate to get $\frac{1}{\sqrt{2}}(|0\rangle+|1\rangle)$ and then I meausred my state. But I always found 1. I expected to find 0 and 1 uniformly random ...
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Does TensorFlow Quantum tfq.convert_to_tensor work on custom gates?

I'm trying to use Cirq with TensorFlow Quantum to simulate a variational quantum classifier. There's a tutorial on the TFQ website on building a quantum neural network to classify a simplified version ...
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Normalization of the quantum state in Cirq

My understanding, for instance from this youtube video, is the following: Assuming a state $\psi = \alpha |0\rangle + \beta |1\rangle$, where $\alpha$ and $\beta$ can be complex. I believe any state ...
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How to learn parameters in a quantum circuit, given an interference pattern?

Using cirq, I have the following quantum circuit, with three parameters: phi, alpha and beta: ...
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Producing $|ghz\rangle\langle ghz|$ State in Cirq

I could manage to produce 3 qubit ghz state in Cirq. But I don't know how I can produce $|GHZ\rangle\langle GHZ|$ in Cirq Here is my code for 3 qubit ghz state Can you help me please for improving my ...
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1answer
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Cirq - Measure Density Matrix Function Getting First Element

Hello I am using measure density matrix function like that: ...
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0answers
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Implementing the HHL algorithm with negative eigenvalues (Cirq)

How do I implement the HHL with negative eigenvalues? This paper (https://arxiv.org/abs/1803.01486) says that: what if $\lambda<0$? This problem actually does not hard to solve, since we can ...
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3answers
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Overview of Cirq, qiskit, q#, ibmq(circuit board), other [closed]

What is the difference between these frameworks or languages? What are the pros and cons of each of these? Do you know any similar framework/platform/language that gives some more advantages?
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1answer
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Cirq-Measuring a State with Rotation Matrix

I have this state: $$p |\text{GHZ}\rangle \langle \text{GHZ}| + (1-p)\rho$$ And after creating this state I have this code lines: ...
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1answer
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Output a Cirq gate as a Numpy array?

How do I output a Cirq gate as a Numpy array? For example, I would like to print a Pauli X gate cirq.X as ...
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1answer
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Multiple Bipartite Entangled State in Cirq

I am trying to create this state: rho = = q . rho_{1,2} + r . rho_{2,3} + s . rho{1,3} + (1-q-r-s) . rho_separable And I wrote this code: ...
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1answer
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Bit Flip, Seperable state and Several Question about Cirq

1)I want to use noise model for my state and bit_flip is not defined on cirq. ...
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1answer
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Cirq: Creating an arbitrary gate for an arbitrary number of qubits

How do I create an arbitrary unitary gate for an arbitrary number of qubits in Cirq? Note: A solution for creating a single qubit gate is answered by Thomas W from this post. How do I create my own ...
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2answers
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How to cite cirq in a scientific article?

What would be the best/prefered bibtex entry for citing cirq ? Is this ok ? ...
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Wrong Expectation value when implementing a VQE for the Heisenberg Hamiltonian

I tried to implement an extended Heisenberg-Hamiltonian as an extra exercise further than my homework. My Hamiltonian is the following: $H = \sum_{NN} \sigma_x\sigma_x + \sigma_z\sigma_z$ I try to ...
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1answer
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XX and YY and ZZ Hamiltonians in vqe

I'm trying to implement a vqe in cirq and I have sort of a brain knot. I have a 4 qubit chain with periodic boundary condition. So in fact a 2x2 qubit grid. Now 2 of them each are coupled. How do I ...
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2answers
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Running Google Cirq example code from their webpage — where do I find information about PROCESSOR_ID?

I'm just ttrying to run the simple example code in Google's Cirq startup page: https://cirq.readthedocs.io/en/stable/google/engine.html I think I have the access authorized correctly via Google's ...
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1answer
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Reordering commuting gates in cirq to reduce circuit depth?

The main functionality for ordering gates in a cirq circuit that I'm aware of is using the predefined insert strategies of cirq.Circuit.insert(). As far as I see, ...
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Create this state using CIRQ Coding language [closed]

I needed help with CIRQ coding as I'm quite new to Quantum Computing. I read the tutorials on CIRQ but don't really understand it. I'd be very thankful if someone could help. A program to create the ...
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Deutsch-Jozsa algorithm: an oracle implementation

I would like to implement the Deutsch-Jozsa algorithm myself using cirq. However, I faced the problem of the implementation of the oracle. I endeavored to apply the Deutsch-Jozsa algorithm for $n+1$-...