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10 votes
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Why is it not a good idea to run Shor's algorithm on a big noisy quantum computer?

Factoring a 2048 bit number with Shor's algorithm involves performing one billion Toffoli gates under superposition (ref). Suppose your superposed Toffoli gate error rate is an amazing 0.01%. Note ...
Craig Gidney's user avatar
  • 37.7k
8 votes
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What is the clear definition of coherent versus incoherent errors?

Coherent vs incoherent: as a rule of thumb, coherent is unitary, incoherent is stochastic. The distinction is not entirely clear when your channel is a mixture of these. Thus, it makes sense to ...
Balint Pato's user avatar
  • 1,053
4 votes

Practical implementation of Shor and other factoring algorithms

I would say that it is not possible to give a proper answer to this question since the problem instances that may potentially be tractable by present-day quantum computers are too small: As ...
Martin Ekerå's user avatar
4 votes
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Are there sources of noise in qubits for which the fundamental origin is unknown?

TLS in superconducting qubits. When you vary the frequency of a superconducting qubit and plot the T1 lifetime you see huge dips in the lifetime at certain frequencies. The dips aren't static; they ...
Craig Gidney's user avatar
  • 37.7k
4 votes

Mathematical justification of postprocessing in QRNG

A QRNG contains some quantum mechanism that produces a sequence of bits $X_1X_2\dots X_n$ which are then post-processed (using a randomness extractor) to produce some final shorter random string $K_1\...
Rammus's user avatar
  • 5,853
3 votes

Qudits in NISQ Devices: Benefits Beyond Dimensional Advantages?

Preamble Versions of this question arise over and over again, probably because most of us are accustomed to thinking that "more is better" rather than "less is more", for example ...
user1271772 No more free time's user avatar
3 votes
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Can Noise in measurements lead to non-zero probability of a state that was not originally in the state vector?

Measurement noise is typically considered a classical outcome that does not reflect the actual final state. For your state vector, if you measure transversally - i.e. you measure, for example, in the ...
Balint Pato's user avatar
  • 1,053
3 votes

What are overlooked noise sources in circuit-level noise?

Often (but not always) leakage errors are not accounted for. A leakage errors occurs if a qubit is excited to a level outside the qubit subspace. Correlated errors between qubits which are not ...
Peter-Jan's user avatar
  • 1,549
3 votes

BP + OSD decoder with both loss and Pauli errors

Expanding on my comment for posterity: the edge weights in MWPM decoders (typically) convert error probabilities to edge weights via the formula $\ln((1-p)/p))$, where $p$ is the probability of the ...
squiggles's user avatar
  • 925
1 vote

Is this quantum circuit design more prone to noise?

The reason why you are seeing inaccurate results on a real backend is because of the SWAP gates. In the current quantum computing hardware that IBM uses, the dominant source of noise is because of ...
Shravan Patel's user avatar
1 vote
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Using Noise Model of a real hardware on qiskit simulators

If all what you want is to derive a noise model from the properties of a real quantum device, then you just need to use NoiseModel.from_backend() method: ...
Egretta.Thula's user avatar
1 vote

How to perform noisy simulation of qiskit fake backends?

The fake backends in qiskit are built to mimic the behaviors of IBM Quantum systems using system snapshots. This system snapshots (or fake backends) contain ...
Shravan Patel's user avatar
1 vote

How to perform noisy simulation of qiskit fake backends?

Qiskit fake backends can be used directly for noisy simulations. For example: ...
Egretta.Thula's user avatar
1 vote

Customed quantum channel definition with Qiskit

This is just a thought and I have not tested this but there is a way to achieve what you want. Make a quantum circuit (call it qc1) with 10 Hadamard gates (for example) on which you would like to ...
Shravan Patel's user avatar
1 vote

Can we somehow relate quantum volume with the total number of gates present in a circuit which the machine can succesfully run without large errors

Quantum volume is a metric designed to quantify the performance and capabilities of a quantum computer. It encompasses various factors like gate fidelity, connectivity, coherence time, and others to ...
Shravan Patel's user avatar
1 vote
Accepted

Clarification on Definitions of Relaxation Probabilities

$P_{T_1}$ is indeed the probability of measuring the qubit in its excited state $|1\rangle$, under the definition above - after time $T_G$ from the moment of excitation. The operators $M_0$ and $M_1$ ...
Ohad's user avatar
  • 1,759
1 vote

What is the clear definition of coherent versus incoherent errors?

The need for these terms might be helpful to understand the intuition. Coherent errors are statistical characterizations while still respecting unitary evolution. Incoherent errors are the traditional ...
Sam's user avatar
  • 187
1 vote
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How can one obtain all calibration data which is needed to plot error_map of the ibm backend from few month ago?

You can simply load the calibration data into the corresponding fake backend, then use plot_error_map with it as follows: ...
Egretta.Thula's user avatar
1 vote
Accepted

How can visualise the old error map of Ibm backend if one save the calibration data of the backend at that time?

You can load the calibration data into the corresponding fake backend. The following function does that ...
Egretta.Thula's user avatar
1 vote
Accepted

RB with Clifford: can I define my own random model?

The core idea of RB is the fact that twirling over the unitary group produces a depolarizing channel, which is what we fit to from the experimental data. However, implementing Haar-random unitaries ...
Banach space fan's user avatar
1 vote

How to run Color code on STIM?

The custom detector error model you're giving is from a totally different circuit. Once you fix that, you're going to run into the issue that the decoder you've chosen (pymatching) can't decode color ...
Craig Gidney's user avatar
  • 37.7k
1 vote
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G-twisted Pauli twirl circuit

It turns out I was misinterpreting $P_{a^\prime}$. This is supposed to be $P_{a^\prime} := G(P_a) = GP_a G^\dagger$. So, the Clifford acts by conjugation instead of only left multiplication. Using ...
epelaez's user avatar
  • 2,895
1 vote
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How many measurements are required to resolve data with a given fidelity?

I haven't read the paper thoroughly, so I'm entirely sure this is accurate, but here's a possibility: Estimating the fidelity in this context (unitary evolution on pure states and projective ...
glS's user avatar
  • 25.4k
1 vote

Does qiskit_ionq have the possibility of simulating quantum circuits with noise?

You can use a noise_model backend option to use a noisy simulator: ...
Spencer Churchill's user avatar
1 vote

How's quantum noise and fault-tolerance related to symplectic geometry and geometric quantization?

Given $p$ an odd prime, the symplectic vector space $(\mathbb{F}_p^{2n}, \omega)$ is a projective representation of the odd prime dimensional $n$-qudit Pauli group. The $n$-qudit Pauli group is a ...
Cole Comfort's user avatar

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