# 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.

186 questions
Filter by
Sorted by
Tagged with
14 views

### How do I perform measurements in the X basis for qutrits in cirq?

After applying the hadamard gate to a 0 state qutrit, I should be able to get it into the + state, but how do I then measure the circuit in the X basis as opposed to the computational basis?
• 33
39 views

### As a completely beginner in Quantum computing, where would I start? [closed]

I have had a keen interest in Quantum computing for a long time but never had the opportunity to learn it. Whenever I search about it to get started, I am getting overwhelmed with the topics, if there ...
9 views

### Expectation values with finite number of shots with qsimcirq

I was using qsimcirq for VQE to obtain exact expectation values of the energy for a certain Hamiltonian with ...
• 473
54 views

### Why does cirq produce a non-positive semidefinite density matrix doing quantum tomography?

While doing quantum tomography in cirq, I ended up getting a density matrix which is not positive semi-definite. Why is this so? Here's the code I used: ...
• 17
49 views

### How to do quantum tomography on a subsystem of 2 of 30 qubits in cirq?

I have a 30 qubit system and I need to do quantum tomography on a subsystem of 2 of its qubit. How can I do this in Cirq?
• 17
1 vote
15 views

### Finding partial trace in CIRQ

Suppose I have a 30 qbit system, due to computational complexity, I can't find the density matrix of the system. But is it possible to find the partial trace of the a sub-system of 2 qubits out of 30 ...
• 17
53 views

### How to compose a larger circuit onto a smaller circuit in Qiskit, adding extra quantum registers to some fixed list

$\newcommand{\ket}[1]{|{#1}\rangle}$ I have a Qiskit quantum circuit for multiplication $M$, that I want to compose onto another qiskit quantum circuit for inner ...
69 views

### How to implement a depolarizing noise channel for qutrits using cirq?

Anyone have any idea how I can implement a depolarizing noise channel for qutrits using cirq? Say using the kraus operators within a class inheriting from cirq.Gate or so?
• 33
1 vote
45 views

### How does the cirq compilation process work?

Cirq compilation process. I cannot find the documentation that describes the internal structure of the library Cirq by Google. There is much information related to high level functions, but none ...
1 vote
23 views

### How to convert a custom observable matrix to a Cirq observable for simulation?

I aim to conduct a Cirq simulation using a custom observable. However, the measure_observables function in Cirq requires an Iterable of cirq.PauliString, making it challenging to directly use a custom ...
• 11
1 vote
63 views

### cirq entanglement qubits

The following code originates from a third-party, although, I have added the commented line containing "UNCOMMENT THE START OF THIS LINE". ...
• 11
1 vote
79 views

### How can we see on Cirq that Google Sycamore has 54 qubits?

Hello, can you explain how to see in Google Cirq that the figure above is a 54 qubits quantum computer ? thanks
1 vote
132 views

### Measuring a specific observable using cirq

I am simulating a circuit in cirq, and I need to measure an observable $$A(\theta) = R^\dagger_z(\theta)XR_z(\theta),$$ and I am not quite sure how to do that. My first thought was to apply these ...
1 vote
92 views

### Need help regarding building a custom VQE

I want to write code for a custom Variational Quantum Eigensolver (VQE) capable of computing eigenvalue(s) for non-Hermitian systems, based on this paper. I have formulated a cost function (provided ...
• 11
123 views

### Initialize circuit by density matrix (i.e. mixed state) by Cirq, Qiskit, QuTip

I want to do a simulation involving: mid-circuit measurement (i.e. based on the measurement result of some qubits to append further gates on other qubits; e.g., Pauli error correction in entanglement ...
137 views

### Variational Quantum Eigensolver (VQE) by scipy minimize in cirq does not work

I tried to make a cirq program calculating an eigenvalue of the observable by VQE. Inspired by the qulacs VQE tutorial, I defined a cost function from the expectation value of the observable with ...
1 vote
68 views

### How to create a 3-D state (array) of qubits in qiskit or cirq etc?

I want a 3-D cube-like array for state of qubits, on which I want further to implement different sets of rotations, etc, for cryptographic means. You can create a 2D grid qubit in cirq with ...
1 vote
54 views

### Tensorflow_quantum hybrid models tf-quantum

I am trying to QCNN for MNIST classification equivalent to that built in. I’m having problems trying to pass my quantum circuit built with cirq as a Keras layer. Here’s what I have: ...
1 vote
198 views

### If Statement OpenQasm 2.0

in the documentation for OpenQasm 2.0 it says one can use an if statement like so: if(c_reg==int) Quantum Operation. However, I would like to execute the following: ...
• 31
49 views

### How to best implement this algorithm?

I am trying to design an algorithm to find a solution to a certain problem. I have N qubits which encode the problem (let's call them the problem qubits) and one check_qubit (which is flipped to |1>...
• 195
314 views

### Controlled NOT gate which flips target when at least one of the control qubits is |1>

I would like to have a controlled NOT gate which flips my target qubit when at least one of the control qubits is |1>. I would like to be able to do this for arbitrary n. For a system with 2 ...
• 195
1 vote
66 views

### Classical control of an entire sub-circuit in cirq

I would like to evolve a quantum state through an entire sub-circuit in my circuit based on classical control. I am aware of the current state of classical control in cirq (https://quantumai.google/...
• 391
1 vote
29 views

### Is there a way to find the computational resources required to perform a simulation of n- qubits in Cirq similar to qsim?

I’m trying to model basic spin chains in 1D using VQE (ideal circuit) with cirq and qsim. The models have between 10-20 sites and varying interactions (nearest neighbour, next to nearest neighbour etc)...
1 vote
37 views

### How to Find a circuit that evolves from one density matrix to another(qiskit or cirq)

given two density matrices, dmBefore and dmAfter, I want to generate(find) a circuit in Qiskit or Cirq that starting initaliazed with dmBefore ends with dmAfter after it's execution. Is it possible?. ...
• 285
85 views

### Cirq seems to output 0 instead of |2> with qutrits

I am experimenting a bit with qutrits on Cirq and came across a problem: my output is 0 when it should be |2>. I defined my qutrit as follows: ...
• 195
172 views

### AttributeError: module 'cirq_google' has no attribute 'Foxtail'

I have installed cirq in my anaconda environment by using the command: pip install cirq When I ran the code below to print the ...
1 vote
307 views

### How to create a multicontrol mcx gate or operation in cirq

In qiskit the method to apply a multi control with more than 2 control qubits is: qc.mct ( listcontrols,targetbit,listancillas, mode=mode[i]) What is the ...
• 285
1 vote
399 views

### Marking a specific quantum state in the oracle function in the Grover's algorithm

I have a simple implementation of Grover's algorithm. As depicted in the results below, the oracle function marks the state |111>. How can I change the Oracle function to mark |010>? ...
• 269
1 vote
197 views

### Resolving AWS-Braket - ValidationException: An error occurred (ValidationException) when calling the CreateQuantumTask operation

I have a quantum circuit for the Markovian Reservoir Engineering[MRE] Model, written in cirq (frontend) and trying to run it on Ionq hardware, using qbraid credits. This is all being done on qbraid ...
185 views

I have been working with on some research on tensorflow, tensorflow-quantum and tensorflow-federated and the problem with that is I just can't install those three at my google colab and I tried ...
• 143
173 views

### Generalizing a brick-wall circuit acting on qubits to acting on qudits

Recently, I have been creating a "brick layer" circuit of random unitary gates (each acting on 2 qubits) which acts on a n qubit register using cirq. A typical circuit looks like this. (...
1 vote
21 views

### Two-time correlators in Cirq?

Is there a way to calculate two-time correlators in Cirq directly? For example, suppose we have an initial mixed state described by a density matrix $\rho_0$, and we want to obtain in our quantum ...
• 234
1 vote
94 views

### Efficient simulation of circuit with variable depth using Cirq

I have a program that needs to evaluate several Cirq circuits by using both simulators the Simulator() and ...
• 234
37 views

### How to take gradient of the tfq.layers.State output?

I am using the following code for building a quantum circuit as a custom tf.keras.layers.Layer: ...
203 views

### How to change the qubits of a cirq Circuit?

I am constructing generic circuits, and I would like to change the qubits after creating the circuits. Is there a way in cirq to do so? for instance: ...
• 355
77 views

### Topmost Universal Gate Based Quantum Simulator?

I am Elijah I'm interested in Drug Discovery and Materials Simulation. I want to purchase a gate based Quantum Simulator for research. I received a proposal. Full State Simulator 30 Qubits on Laptop, ...
113 views

### how to flatten a cirq.Circuit with CircuitOperation

I have a cirq.Circuit that uses a CircuitOperation, something like: ...
• 355
1 vote
91 views

### How can i describe Custome Gate Sets in Cirq?

i try to create a Custome GateSet with the CompilationTargetGateset class but it does not work. ...
• 191
1 vote
35 views

### Is there a method in pyQuil to create logical boolean gates

is there another way to represent a boolean gate. The straight forward way would be to define a gate my a matrix and then apply this gate to the circuit. What i mean by that? For Example an AND-Gate ...
• 191
1 vote
102 views

### Convert an integer to its basis state in Cirq

I am trying to implement Quantum Adder using QFT in Cirq. I previously did the same problem using Pennylane, in which I converted an integer into its Basis state using the BasisStatePreparation method ...
1 vote
152 views

### How to rewrite this Cirq problem into Qiskit?

I have a following example problem in Cirq, representing a very simple operator given by  \hat{H} = a^\dagger_0a_2 + a_0a^\dagger_1 + 0.9\, a^\dagger_0a_1a^\dagger_2a^\dagger_3 + a^\...
• 264
186 views

### Merge two Y**0.5 gate into a single Y gate

How can I merge two consecutive cirq.Y**0.5 gates into a single cirq.Y gate with a transformer? I can use ...
• 505
1 vote
84 views

### Two Qudit custom gate error in Cirq

I am trying to build two qudit CX (d-dim) gate. and getting below error. There is no issue in the unitary matrix. Please suggest to resolve the error.
• 15
114 views

### Interpretation of Qudit measurement output in cirq

Here [+1] represents X gate for qutrit. How the Counter value is coming to 5? which is the measurement outcome(q0q1q2->102). Even for (q0q1q2->101) also counter value is 5. In total, for this 3 ...
• 15
1 vote
328 views

### How we can perform measurements on an X, Y or Z basis in cirq?

How we can perform measurements on an X, Y or Z basis in cirq? Is there any function where we can give the list of qubits and measurement basis as an argument and get the output?
79 views

### Printing Stabilizer State of a circuit using Cirq

How to print the stabilizers for a given circuit using Cirq (just like in Qiskit)? For example, if I have the following cluster state and make a circuit using Cirq. I give the circuit as input, and I ...
49 views

### Why importing cirq_ionq gives an unexpected argument error

I'm trying to install cirq_ionq, a python library for running cirq circuits on IonQ's quantum hardware. However, when I try importing it I get an unexpected argument error: ...
407 views

### is cirq suitable for simulation of quantum error correction?

I experimented with stim and qiskit for QECC simulations. They both have limitations : for example stim has no support for non-clifford operations (qiskit does); qiskit has no support for multiple ...
• 2,217
145 views

### $S^2$ expectation value of a circuit seems wrong

I need to rewrite a following circuit from Cirq to Qiskit with $2\varphi = \pi$. It's a circuit representing an initial state for VQE calculation. Considering, that ...
• 264
1 vote