Questions tagged [experiment]
For questions related to experiments with actual quantum computing devices and how to interpret their results. Also appropriate if the question can only be reasonable answered with an experiment (or experiment design).
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When is a quantum algorithm considered to have a significantly superior performance over another quantum algorithm?
Suppose we have two heuristic quantum algorithms $A$ and $B$ that attempt to solve a certain class of optimization problems. Let's suppose that the benchmarking metric is Time To Solution (TTS), which ...
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What is the purpose of Doppler cooling in neutral atom devices?
As a theorist without much experimental physics background, I am reading some reviews to understand how these systems work. I've learned that one needs to use Doppler cooling before trapping the atoms ...
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Randomness and precision of Quantum Number Random Generators
I am reading about the problem of generating random quatum numbers, and I am interested in the state of the art in terms of the true randomness these generators achieve.
As far as I know, following ...
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Is quantum energy teleportation a specific version of quantum teleportation?
I just read another sensationally titled article in Quanta magazine, Physicists Use Quantum Mechanics to Pull Energy out of Nothing where they discuss the work of Masahiro Hotta on transferring energy ...
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What is a gate-level circuit used in the 2022 Jafferis et al. experiment on Sycamore?
A recently published Nature paper of Jafferis et al. describes an experiment with a handful of qubits performed on Google's Sycamore processor to explore the SYK model in the context of AdS/CFT and ...
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Does it make sense to compare different quantum computer technologies?
Let's assume I have some quantum program I tested and tuned on a simulator and that now I want to see how it actually performs on real quantum hardware. I test it on IBM Superconducting devices and ...
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Publicly available samples for quantum circuits and/or simulators
With Yosi Rinott and Tomer Shoham we studied various statistical aspects of samples coming from NISQ computers.
My question is about available data consisting of samples from NISQ computers
We would ...
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Is there an alternative algorithm to extract a probability of states of qubit after measuring?
Let a simple quantum circuit consist of one qubit and one classical bit. Initially, a qubit has the $|0\rangle$-state and then goes through some sequence of quantum gates, see the circuit below.
The ...
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Suggestion on reading resources on superconducting quantum computing
I am a physics student who works with NMR spin-based quantum computing, now branching into superconductor-based qubits. So I am reading lecture notes by Nathan K Langford and Steve Girvin. I can ...
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Can the paper by Monz et al. (2015) be regarded as a real implementation of Shor's algorithm?
I'm studying about the Shor algorithm and I wonder whether the paper below can be regarded as a real implementation of the Shor algorithm:
https://arxiv.org/abs/1507.08852
In this paper, they tried to ...
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Good review articles on microwave hardware for superconducting qubit quantum computing?
I am trying to find some review articles on the microwave hardware used in superconducting qubit quantum computing.
So far, most papers that I found seem to be high level overviews, e.g., Multilayer ...
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How big is the Hilbert space of a boson sampling experiment?
Boson sampling experiments are typically characterized by two key parameters: the number of photons $M$ and the number of modes $N$.
A recent experimental demonstration (arXiv:2106.15534) with $M = ...
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'Internal error. Error code 9999' when running job on IBMQ
I'm trying to run a series of circuits in a job and I keep getting this error message which I haven't been able to find the meaning of anywhere in qiskit's documentation, online, etc. The job appears ...
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Can entangled photons create entanglement in material particles?
Is it possible that two entangled photons when absorbed by two material particles, say two atoms, lead to the entanglement of these atoms? Is there any published research on this topic?
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How to quantify trace distance between two matrices representing two quantum optical networks?
This is my first post here, so I'm sorry if this question could be ill-formulated. I have performed measurements on a 12x12 optical quantum network, so that I have a stochastic matrix $P^{exp}$ where ...
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Working with higher energy states in Qiskit Experiments
I'm looking at the source code for the Qiskit Experiments module and see that the EFRabi class subclasses the Rabi class with the intent of calibrating rotations between the 1 and 2 states instead of ...
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Why is it important to perform optical quantum computing with ONLY linear components?
The main achievement of the KLM protocol is demonstrating that quantum computing can be done with only linear optical elements, i.e., beam splitters, phase shifters, single-photon sources, and photo-...
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In the job tab, no histogram appears
(Newbie here) Accessing IBM Q Experience on a Windows 7 operating system and using the Google Chorme browser. I can completely assemble my circuit, using the IBM Quantum Composer and when executing it ...
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How can I resolve this get_count issue from running multiple circuits?
I'm running a couple of circuits at the same time using an array of variables. However, I met an issue regarding accessing the counts. Here's part of the code I have:
...
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Return outputs with zero counts
I am running a simple 3 qubit circuit which produces the following results:
{'000': 5, '001': 3, '010': 10, '100': 5, '101': 7, '110': 7, '111': 4}
There are no ...
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Is there a measurable of entanglement for a many-body system?
After having a discussion with a quantum computing colleague, a question came up: is there any meaningful way to measure entanglement (or something related to it) in a solid-state many body system ...
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What is the executable opcode for Qiskit quantum hardware, as the quantum circuits or the transpiled/compiled QObj/ QASMQObj are assembly languages? [duplicate]
When we write a QASM code or build quantum circuit on Qiskit GUI, it converts it into QObj/QASMQObj (refering paper Qiskit Backend Specifications for OpenQASM and OpenPulse Experiments) or its ...
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What experiments can distinguish between mixed and pure states?
To distinguish between a coherent and de-cohered stage of the same system
what experiments can provide the answer? The term Experiment is used here in the Bohr-Einstein-debate sense, a realizable ...
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Where does the energy go in a Power Rabi experiment with superconducting circuits?
When performing a Power-Rabi experiment, e.g in superconducting circuits, we are playing a pulse to a qubit and then reading out its state by playing another pulse to a dispersively-coupled readout ...
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What does "decoherence attenuates the density matrix" mean?
I'm reading the paper Implementation of the Quantum Fourier Transform. On page 4, they write
To a first approximation, decoherence during the course of the QFT attenuates the entire density matrix. ...
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Changing one qubit causes changes in another independent qubit on ibmqx2 in IBM Q Experience
When I run this program on ibmqx2 (the backend matters) in IBM Q Experience, the results are interesting. Essentially, the program measures the error rate on $|q_0\rangle$ after fiddling with $|q_1\...
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Writing twice to same classical register -> 1 for some backends in IBM Q Experience
On some backends, measuring the same expected value twice to the same classical register always leaves that classical register in the "1" state. I don't know if these results will hold over time, but ...
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Reversal of time arrow on IBM Q
It is well known that a quantum computer is reversible. This means that it is possible to derive an input quantum state $|\psi_0\rangle$ from an output $|\psi_1\rangle$ of an algorithm described by a ...
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Simple program produces consistently skewed results in IBM Q Experience
I'm running this program (essentially a two bit random number generator) on ibmqx2 in IBM Q Experience. The backend matters. Other machines give unexpected results, but the graph looks different for ...
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What is the difference between classical and quantum computers as well as computing (permuting) itself?
Theoretically and for sure physically (I know the quantum physics behind it) I know something about it. But not that much. That's why I ask the question here. I'm very interested. The only answer to ...
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Is manual or automated error correction more practically promising in the near term?
I'm curious if there's any consensus on this question among actual practitioners, but please feel free to close it if it's hopelessly opinion-based (since we've only taken baby steps toward the ...
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Quantum Supremacy: Some questions on cross-entropy benchmarking
I was skimming through the Google quantum supremacy paper but got stuck on this section:
For a given circuit, we collect the measured bit-strings $\{x_i\}$ and compute the linear XEB fidelity [24-26, ...
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given an EPR pair, how do I calculate expectation value?
given A and B share EPR pairs $ (|00⟩+|11⟩)/√2$
both are free to measure their own qubit with the following measurement settings
A measures with $[ |0⟩, |1⟩ ]$
B measures with $[ sin(3π/8)|0⟩ + cos(...
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IBM's quantum computing capabilities — entangled 18-qubit GHZ states and high coherence times
Here's a blog post that corresponds with what IBM presented at the 2019 March Meeting.
In this post, they claim they've measured qubit T1 relaxation times above 500 microseconds, and claim that they'...
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Measuring Ising anyons: What is a fusion measurement?
I have several doubts about measuring Ising anyons. Measurement is crucial for quantum computation and even more so for magic state distillation which is necessary to make Ising anyons universal.
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Can one make NV centred type qubits from analogus materials in the periodic table?
Can one replace Nitrogen with Phosphorus and Carbon with Silicon and so on?
What would be the conditions that would preclude such a realisation? Are there any implemenations so far?
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Spin precession using a laser
According to Christopher Monroe: "Modular Ion Trap Quantum Networks: Going Big", the hyperfine states of the valence electron in the Yb+ is used as a qubit. I know that we can change the spin ...
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Can "experimental data from a quantum computer" be used to test separability probability conjectures?
An article entitled "Experimental data from a quantum computer verifies the generalize Pauli exclusion principle" by Scott E. Smart, David I. Schuster, and David A. Mazziotti has just appeared
In the ...
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What is the significance of recent demonstration of a passive photon–atom qubit swap operation?
In reference to this recent nature article: https://www.nature.com/articles/s41567-018-0241-6
Specifically, does this warrant a new type of gate?
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State of the art gate speeds and decoherence times
I am interested in the state of the art gate speeds and decoherence times for the qubit types I know are being pursued by companies presently:
superconducting qubits,
ion trap qubits,
photonic qubits....
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Breakthroughs in quantum computing using non-standard quanta [closed]
It seems that quantum computers can be classified by the type of quantum they operate on. Not entirely sure what category most common current systems fall into (eg. D-Wave, Google, IBM, Microsoft). ...
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Is "probabilitistic,universal, fault tolerant quantum computation" possible with continuous values?
It seems to be a widely held belief within the scientific community that it is possible to do "universal, fault-tolerant" quantum computation using optical means by following what is called "linear ...
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Will Moore's Law be no longer effective once quantum computers are created? [duplicate]
Moore's law states that computer power doubles in every 18 months (more formally: "the number of transistors in a dense integrated circuit doubles about every two years."). Statistics suggest that ...
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Rotating about the y- or z-axis of the Bloch sphere
In order to rotate about an axis of the Bloch sphere we ususally use pulses e.g. in trapped ion quantum computing or superconducting qubits. Let's say we have rotation around the x-axis. What do I ...
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Conditional Phase Gate Superconducting Qubits
In the paper "Demonstration of two-qubit algorithms with a superconducting quantum processor" (L. DiCarlo et al., Nature 460, 240 (2009), arXiv) they demonstrate how to realize conditional phase gates ...
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Is PostBQP experimentally relevant? [duplicate]
Far from my expertise, but sheer curiosity. I've read that PostBQP ("a complexity class consisting of all of the computational problems solvable in polynomial time on a quantum Turing machine with ...
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What is the status of confirming the existence of anyons?
In a comment on my answer to the question: What exactly are anyons and how are they relevant to topological quantum computing? I was asked to give specific examples of occurrence of anyons in nature. ...
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Translation of color/toric code to a small network of solid-state spins
Within Quantum Error Correction and stabilizer codes, toric codes/surface codes are very tempting, mainly for their high error threshold. For more background please check up, in our Physics sister (...
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Active improving of nanodiamond surfaces for NV centers?
This question is related (and complementary) to "Passive improving of nanodiamond surfaces for NV centers?".
Nitrogen-Vacancy centers (NVs) have astonishing quantum properties, which make them ...
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Passive improving of nanodiamond surfaces for NV centers?
Nitrogen-Vacancy centers (NVs) have astonishing quantum properties, which make them interesting as potential hardware both for quantum computing in particular and for quantum technologies in general. ...
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