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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What are physically allowed CNOTs for Rigetti's 19 qubit chip and Google's 72 qubit BristleCone chip?

For each IBM quantum chip, one can write a dictionary mapping each control qubit j to a list of its physically allowed targets, assuming j is the control of a CNOT. For example, ...
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1answer
364 views

Is there a mistake in the VQE Ansatz in Cirq's tutorial?

I have been going through Cirq's VQE background tutorial and after examining the Ansatz it seems to me that the only layer that actually affects the final measurement is the rot_x_layer. The other ...
6
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1answer
462 views

Why is this implementation of the order finding algorithm not working?

I asked a question about this earlier, but I am still coming across problems in my algorithm implementation. I am trying to implement the order finding algorithm on Cirq finding the minimal positive $...
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1answer
444 views

List of qubit locations with cirq

As far I understand, qubits in cirq are labelled by their positions on chip. For example print( cirq.google.Foxtail.qubits ) yields ...
5
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1answer
130 views

Where does the Xmon simulator from Googles cirq framework its entropy from?

Measurements create entropy as we all know. But computers themselves are deterministic machines. Most devices use processor heat as a source for random number generation as far as I know - which has ...
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3answers
106 views

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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2answers
563 views

How to prepare a specific initial state of three qubits?

I would like to prepare the following initial state for variational quantum algorithms: $$ \sin\theta_1 \sin\theta_2 \sin\theta_3 |000\rangle + \sin\theta_1 \sin\theta_2 \cos\theta_3 |001\rangle + \...
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3answers
3k views

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?
4
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1answer
364 views

N-Toffoli on Cirq

I am looking for guidance in more generally how to developed n-bit gates in Cirq. I am working on a QNN paper and I need to develop a n-controlled gate to be able to measure the cost function of the ...
4
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1answer
537 views

Creating an ansatz for variational quantum algorithms?

I was recently reading through the tutorial on the Cirq documentation about creating variational quantum algorithms, and I came to the section on ansatz preparation. The way that the ansatz is ...
4
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1answer
596 views

How to set a starting state in cirq?

I'm learning how to use the cirq library. Every time I set up a circuit the starting state of the qubits is $|0000..0\rangle$. Is there any way to make the starting state different? I'm thinking of ...
4
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3answers
821 views

How do I create my own unitary matrices that I can apply to a circuit in Cirq?

I am trying to simulate Deutsch's algorithm, and I need to apply the oracle function matrix to my circuit.
4
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1answer
165 views

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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2answers
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How is $X^q$ equal to $RX(\pi q)$?

I've seen in google cirq that a $X^q$ gate is converted in openqasm to $RX(\pi q)$, why is that? Same for $S^q$ into $RZ(\pi q/2)$.
4
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1answer
232 views

How to add noise to existing gates in Cirq?

I would like to add noise to existing gates in Cirq, i.e. to define something like NewGate = cirq.Gate(qubit) followed by ...
4
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1answer
186 views

Moments-based quantum circuit in Cirq

In Cirq, quantum circuit consists of moments, which in turn consists of operations. This is different from Qiskit/OpenQASM, which doesn’t have the concept of moments. What is the design philosophy ...
4
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1answer
268 views

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 ...
4
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1answer
135 views

Using parametrised values and 'Symbols' in Cirq

I'm just wondering how one should go about using parametrised values and the Symbol object that gets resolved at runtime? For example, if I would like to implement the gate $R_x(\theta) = e^{-i\theta/...
4
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1answer
45 views

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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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-...
3
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1answer
883 views

How to add control to gates in Cirq?

My question is very simple. I know there is a method to add a control to previously defined gates. I saw in the API of cirq that there is a command Controlled gate (here). I'm not understanding though ...
3
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1answer
95 views

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 ...
3
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1answer
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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 ...
3
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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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1answer
75 views

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
55 views

cirq.Ry complains that it needs one argument

When I try to put an Ry gate into my circuit in cirq, I get an error saying that it only takes one argument. ...
3
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1answer
164 views

cirq.ControlledGate from sub-circuit generator

In Cirq, is it possible to take a sub-circuit generator and use it as the sub_gate in a cirq.ControlledGate? ...
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Estimate run time of Cirq circuit on forthcoming Google quantum computer

Calling cirq.Simulator().run(..) on your circuit to get an idea of how it'd behave if you were to run on Google's (apparently) forthcoming real hardware is fine and dandy. Is there a way to estimate ...
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142 views

Quantum Optimization via Quantum Label Classification in Quantum Circuits

I have been reading Farhi and Neven's paper on quantum neural networks on quantum circuits. I also found an example - albeit not ideal as pointed out by a couple of users - thank you - in here. ...
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0answers
107 views

Measuring the expected energy of a quantum circuit

I implemented the following circuit: I am interested in measuring the expected energy of the circuit. I am using Cirq. I am wondering what are the next steps. Sorry if the question seems very basic, ...
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2answers
281 views

GridQubit in Cirq vs LineQubit

It's perhaps a very silly question, but in what ways is it advantageous to use GridQubit vs LineQubits to develop quantum circuits? Specially to develop ansatz ? Are GridQubits Cirq's way of ...
2
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1answer
131 views

Cirq - Print state of qubit

Seeing a state of qubit is too complicated in Cirq I don't want to simulate, I would be happy for debugging, to see the probability/ amplitude of the state of a qubit, without measure and simulate ...
2
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1answer
35 views

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 ...
2
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1answer
65 views

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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2answers
127 views

How to cite cirq in a scientific article?

What would be the best/prefered bibtex entry for citing cirq ? Is this ok ? ...
2
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1answer
209 views

Is this the correct quantum circuit for the order-finding algorithm?

The algorithm is being implemented on Cirq, with the goal of finding the smallest $r$ for cooprime numbers $x$ and $N$ satisfying the equation $x^r \ = \ 1($mod $N)$. I have set $x \ = \ 2$ and $N \ = ...
2
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1answer
153 views

Building a state with parallel execution

I'm trying to implement the main algorithm described in the Quantum Recommendation Systems paper. In order to do this, I have to create a quantum state $|x\rangle$ corresponding to a real vector ...
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0answers
45 views

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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0answers
90 views

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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0answers
65 views

A bug during CIRQ installation

I had the following problem with an installation of the Cirq. When I typed python -m pip install cirq, I got the following line: "Cannot uninstall 'sympy'. It is ...
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0answers
114 views

Cirq: Any interesting introductory level example using 2D grid of qubits?

I have already asked this question on reddit.com/r/QuantumComputing. Cirq supports to create quantum circuits composed by qubits having 2D grid structure. We have been preparing educational ...
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0answers
94 views

Would this quantum algorithm implementation work?

I am trying to implement the order finding algorithm on Cirq finding the minimal positive $r$ for coprime $x$ and $N$ satisfying the equation $x^r \ = \ 1$(mod$ \ N$). In my case, I have set $x \ = \ ...
2
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1answer
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Is it possible to create controlled gates with an exponent in Cirq?

Is it possible to create controlled gates with an exponent in Cirq? For example, a controlled $\sqrt Z$ gate.
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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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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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1answer
44 views

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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2answers
106 views

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
157 views

Computing circuit depth in Cirq

I ran into a problem of how to extract circuit depth from Cirq circuit object. In Cirq circuits consist of a list of Moments. Number of moments is not equal to the circuit depth in general case. I ...