Questions tagged [noise]

For questions about different types of noise a quantum computer (or qubits) may experience; how this affects the outcome of the computation; how to reduce a specific type of noise on a specific implementation of quantum computer; or how to simulate noise.

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Does Qasm Simulator add noise by default?

I am wondering if Qiskit QasmSimulator adds noise by default or not. I am asking because I have 2 circuits: circuit 1: computes cosine similarity between two vectors circuit 2: computes cosine ...
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Cirq: Getting The Instances (samples) of a Quantum Circuit with Probabilistic Unitaries or Mixtures

The wavefunction simulator in Cirq uses a Monte Carlo approach to simulate a certain subset of quantum noise channels, namely through probabilistic/stochastic application of unitary gates. These are ...
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Does qiskit_ionq have the possibility of simulating quantum circuits with noise?

I'm using qiskit_ionq API for simulating quantum circuits on ionq devices. Currently, I'm using the ionq_simulator backend, but I think it performs noiseless ...
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Additivity of degradable and anti-degradable quantum capacities

It is known that for degradable channels $\mathcal{N}$ and $\mathcal{M}$, the single-letter quantum capacity is aditive (Potential Capacities of Quantum Channels), i.e. \begin{equation} Q^{(1)}(\...
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Noise model correspondence to qiskit implementation for $CNOT$ gate

My question especially relates to the CNOT because I'd like to carefully understand how Qiskit simulate a CNOT model. Specifically, from my understanding, two independent qubits are affected by a ...
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Readout Error in Qiskit: What is a reasonable model?

The Readout Error in Qiskit is described here: https://qiskit.org/documentation/stubs/qiskit.providers.aer.noise.ReadoutError.html Although it is easy to obtain such an error for 1-qubit for IBMs ...
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How to merge logical computation with encoding-decoding schemes

Usually QEC is treated in two different ways. Definition of a logical computation with a non-destructive QEC scheme Definition of a encoding-decoding scheme with destructive measurement after ...
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Implementing Readout Error in my circuit seems to have no effect whatsoever

I am trying to perform a simulation using Qasm in order to see how the readout error actually affects my circuit. The circuit I am implementing is a trivial one, the three qubit one that implements ...
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What makes dynamical decoupling a good method since the fidelity after using it can only reach 0.85 or so?

From this paper, I see that the fidelity of single qubit gate after using dynamical decoupling only reach around 0.85 while I normally saw experiment papers state their fidelity can reach around 0.99 ...
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How does an $\sqrt{X}$ error propagates through an $T$ gate?

I wonder whether there is a compact way of describing a noise $\sqrt{X}$ propagating through a $T$ gate. Possibly in terms of Pauli and/or Clifford operators.
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What traces can be estimated in DQC1 (One clean qubit model), and how?

In particular I'm hoping to understand what is written in this paper better: https://arxiv.org/abs/quant-ph/9802037 (On the Power of One Bit of Quantum Information, Knill and Laflamme 1998) In the ...
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Qubit dephasing times

The dephasing time (also known as decoherence time in the literature), $T_2$, speaks about the timescale in which qubits experience dephasing effects. This relates with the decay of the off-diagonal ...
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Fail to add amplitude damping error to NoiseModel

I am reading a book named Learn Quantum Computing with Python and IBM Quantum Experience authored by Robert Loredo. When I tried to run the code on Chapter 11, I followed the instruction and wroted ...
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2 answers
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Proven quantum advantage (in the algorithmic sense) without error correction (for specific algo, or noise models)

I would like to know if there are some specific class of quantum algorithms, under some hypotheses about the noise model behind the quantum gates for which we know that there is an exponential ...
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Add noise_model when using 'ibmq_qasm_simulator' backend and provider.runtime.run() function

I am trying to test some qiskit code that employs readout-error mitigation using the ibmq_qasm_simulator backend and Qiskit Runtime. I am getting the backend as ...
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Paper on geometry of 2-level Quantum states influenced by noise

Are there papers discussing geometry of quantum states (especially two level systems) influenced by noise.
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Calculating bit flip and phase error using local operations for GHZ state

Suppose each qubit of $\text{GHZ}_3$ State is distribute to $3$ different parties at different locations through a noisy quantum channel. So each qubit can possibly go through: a bit flip error, a ...
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Implementing Noise in Pennylane (using qiskit.aer)

I want to implement noise in Pennylane using qiskit as a plug-in. I found this tutorial from Pennylane. But, when testing it the bit-flip error seems to have no effect at all. Here, I made some slight ...
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Cirq error models

I have two questions about error channels used in Cirq to model noise quantum circuits. The first one is that for the deplorizing error model, one common setting is to set larger error rates for two-...
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Is it overestimating noise in a QPU if we use infidelities and also quantum channel such as depolarising or amplitude damping?

I have mainly seen two ways of studying noise in quantum algorithm simulation. The first one is to suppose that your quantum gate can be implemented with a probability of success of $\mathcal{F}$ (...
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Is D-Wave advantage a noisier hardware compared to the older D-Wave 2000?

Is D-Wave Advantage noisier hardware compared to the older D-Wave 2000? There is any measure of the noise within the vendor's whitepapers, the quantum annealer analogue of e.g. decoherence time, ...
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Error Model on id gate, is not giving any error

I am trying to play with NoiseModel of qiskit, and I noticed that error on id gate is not giving any error results, while error ...
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Bias in the results of superposition measurements on IBMQ Backends, qiskit

Dear people on this forum, I was doing some research, and I created this circuit in qiskit Please bear in mind that I am really new to this field, and I do not retain much knowledge yet. Therefore I ...
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2 votes
1 answer
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Accuracy of Grover algorithm is 100% for 2 qubit, 94.5% on 3 qubit and 96.2% for 4 qubit on simulator. Why it decreasing and then again increasing?

The accuracy of Grover's algorithm decreases for 3 qubit then increases for 4 qubit and then again increases for 5-qubit on simulator (qasm simulator) with pi/4(sqrt N) iterations. What is the reason ...
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3 answers
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Why does making a quantum circuit more noise resilient make it easier to simulate classically?

I was reading Quantum Computing in the NISQ era and beyond (John Preskill, 2018) but I didn't get this point on pages 9-10: There is a substantial opportunity for experimentalists and theorists, ...
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4 answers
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Simulating a quantum circuit with decoherence and noise

Based on the answers given here and here, it is pretty clear that an arbitrary quantum circuit can be simulated with matrix algebra. The difficulty is that this assume perfect fidelity. I am unsure ...
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1 answer
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Simulators vs Real Backends

I am using Qiskit to run some circuits and a question arises in my mind. I know that when we run in the simulators we are running in "ideal" environments. This means there is no noise that ...
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Does noise model in qiskit impact the optimized parameters for QAOA?

I have read this paper about the effects of quantum noise on QAOA. In the conclusion, it says: QAOA is a noise-tolerant algorithm, quantum noise does not change the QAOA quantum circuit parameter ...
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3 votes
1 answer
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Special properties of a channel whose Kraus decomposition contains Identity

I would like to know if there are any special properties of channels that permit a Kraus representation that includes an identity? That is, if I am given a Kraus representation of a CPTP map $\Phi$ ...
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How to differientate the noise functions in qiskit?

In Qiskit, there are many different Quantum Error Functions. From my understanding, pauli_error represents the error rate of $X, Y, Z$ independently, and ...
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Is it possible to use the mitigation process on a teleportation circuit?

Is it possible to use the mitigation process on a teleportation circuit? Sorry, i'm still starting, if someone can get me out of this doubt, I would appreciate it. The circuit I'm trying to make this ...
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Is noise the only reason that makes the results of Quantum Support Vector Machine (QSVM) and Classical SVM differ, when we use a large dataset?

When I used and tested out the Quantum Support Vector Machine for just 120 samples of a large dataset (Training - 100 and Testing - 20). Its kernel classification results were quite close to the ...
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4 votes
1 answer
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If there is quantum noise, can a time interval be short enough that only one-qubit errors (eg. as in the Shor code) occur?

The Shor code can be used to protect against an arbitrary one-qubit error. If the time interval over which quantum noise acts is short enough, can it be assumed only one-qubit errors occur, so one ...
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1 answer
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unexpected effect of coherent unitary error in qiskit

I'm trying to simulate the effect of a coherent unitary Z rotation at an arbitrary angle of a single qubit on the fidelity of a quantum circuit. I am using the qiskit Aer noisy simulator. More ...
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2 votes
1 answer
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Noise-induced amplitude amplification?

I wanted to share some results from an experiment which I find thought were deeply surprising. The basic idea is to prepare a superposition in a main register then conditionally apply lots of random ...
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4 votes
3 answers
449 views

How are eavesdroppers detected when using BB84 in the presence of noise?

I would like to expand upon this question: What is the probability of detecting Eve's tampering, in BB84? Let's say that when the receiver (colloquially referred to as Bob) receives a qubit and ...
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5 votes
2 answers
336 views

Determining whether there exists an equivalent set of unitary Kraus operators

I have a CPTP quantum channel $\mathcal{E}$ that I've characterized by an operator sum representation $\{E_i\}$ for $i=1, \dots, m$ which acts on an input state like $$ \mathcal{E}(\rho) = \sum_{i=1}^...
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2 votes
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How do you quantify the figurative 'cost' of a quantum circuit

Many gates are not available on a real computer and therefore the circuit must be transpiled into a specific set of gates. I have seen this equation below which is used to to determine the 'cost' of a ...
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1 answer
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What are examples of Kraus operators describing the process of control error?

Noise, such as photon loss or dephasing, is often described with Kraus operators. Are there examples of Kraus operators describing the process of control error?
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understanding final state of a QPU interacting with the environment

As stated in UT's QML course for a QPU that is interacting with the environment: The environment is defined by a temperature $T$, and if we let the system equilibrate, the QPU will become thermalized ...
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2 votes
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How to turn a 'term' in a QuantumError into a QuantumError?

A QuantumError class may have many terms, and we can use .error_term(position) to have a look at each term. But it returns a list instead of another QuantumError ...
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2 votes
1 answer
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Graph States subjected to finite erasures

The appendix to the paper Graph States as a Resource for Quantum Metrology states that when graph states subjected to finite erasures, $$G\Rightarrow Tr_\vec{y}G.$$ While more explicitly he explains ...
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2 votes
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Iterative Phase Estimation with noise vs standard Quantum Phase Estimation with noise

I am doing Qiskit Lab 4 about Iterative Phase Estimation. I created a circuit implementing IPE for theta = 1/3 (phase of 2pi/3). Here's the circuit: It seems to do okay if I run it without noise in a ...
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3 votes
1 answer
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Can quantum error correction work on any type of channel?

It says on wikipedia that quantum error correction can (at best) correct phase flips and bit flips. A popular form of representing a quantum channel is in its Kraus representation (scroll down to ...
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3 votes
1 answer
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noisy circuit by openfermion

I am working on designing quantum error mitigation algorithms for simulating chemical systems. Therefore, a necessary component is to add noisy to the ideal circuit when using a quantum simulator. But ...
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4 votes
1 answer
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Is un-computing $U$ a good proxy for circuit fidelity?

I'm trying to estimate the fidelity of some family of unitaries $U(\theta)$ implemented on a noisy quantum computer. To do so, I start from an uninitialized state $|0\rangle$ and run the circuit $U(\...
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4 votes
1 answer
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How can I fit an unknown quantum channel?

Suppose that I have one noisy channel $\mathcal{E}$ and I want to fit it with another one $\mathcal{E}_0(p)$ that depends on some fitting parameter $p$. As both of this processes for me are ...
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Qiskit: simulate a circuit using a backend noise model

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3 votes
1 answer
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What are the possible gates that I can use to vary input states before CNOT?

We know that the noise of the $\text{CNOT}$ gate varies depending on the input state before it. What are the gates that I can put in the place of the 4 identity gates above to change the input state ...
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2 votes
1 answer
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Is Noise model for quantum prototypes accurate in Qiskit

We know that in Qiskit noise models modeling specific quantum machine prototypes exist and can be inserted into the code. However, are these models fixed in nature or they continuously improve ...
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