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Questions tagged [experimental-realization]

For questions about physical implementations of a quantum algorithm or other quantum information protocol. DO NOT use for questions about simulation or emulation of quantum computers, or cloud-based quantum computing services like the IBM Q Experience.

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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 ...
agaitaarino's user avatar
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9 votes
0 answers
188 views

How can time crystals be useful in qRAM design?

A time crystal is a phase of a matter which is ordered in time, similar to classical crystals which are ordered spatially. In other words, the structure of a time crystal is ever-changing but with ...
Martin Vesely's user avatar
8 votes
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282 views

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 ...
Mark Spinelli's user avatar
8 votes
2 answers
587 views

What design considerations set the frequency bounds for superconducting qubits?

Superconducting qubits generally have frequencies within the range of 4 - 8 GHz. What design considerations give the upper and lower bounds for what is a feasible design. I.e, why can't they be higher ...
psitae's user avatar
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8 votes
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What are the main obstacles to overcome to build silicon-photonic quantum computers?

In superconducting quantum computers, we use mostly superconducting qubits or trapped ions. However, those systems are quite large because their environment either requires near absolute zero ...
Aleksandar Kostovic's user avatar
8 votes
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368 views

In D-Wave's universal quantum computer, why does the YY term have to be driven along with the linear X term?

D-Wave has a new prototype annealer that uses a Hamiltonian which, if there was enough qubits and sufficient control, would be able to simulate any universal circuit-based quantum computer with at ...
user1271772 No more free time's user avatar
7 votes
0 answers
121 views

Qubit fidelity of DWAVE device

Since DWAVE quantum device is constructed using superconducting flux qubits, each qubit cannot be produced identically so that the fidelity of the qubit must be different. DWAVE only provides the ...
peachnuts's user avatar
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7 votes
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How to decide which quantum device to use if a quantum algorithm is given?

I'm planning to write my master thesis in quantum computing. The subject of the thesis is to find out which attributes (properties, features) of quantum algorithms respectively their implementations (...
krsp's user avatar
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5 votes
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How do we realise photonic gates?

I am interested in photonic computing, and I am curious how the gates work. I once saw a picture of a photonic CNOT gate that used just mirrors and polarizers. I have not been able to find any ...
Spock's user avatar
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5 votes
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89 views

Are single photons necessary for this quantum autoencoder implementation?

The following diagram is from Experimental Realization of a Quantum Autoencoder: The Compression of Qutrits via Machine Learning How this setup works: What will be obtained from this set up is the ...
Sam's user avatar
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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 ...
MonteNero's user avatar
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Probability of error in BB84 if Eve is using Breidbart's basis

I'm taking a course on quantum cryptography and I have a homework to calculate probability of error in BB84. The task says to assume that Eve uses the Breidbart basis with eigenvectors $$|φ_0⟩ = \cos(...
demonsrun's user avatar
4 votes
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What are currently the best reported qubit error rates per gate operation?

Based on some investigation, I have found the best qubit coherence timescales, in superconducting architectures, to be the order of milliseconds. https://journals.aps.org/prb/abstract/10.1103/PhysRevB....
user111's user avatar
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How are measurements done exactly on IBM cloud computers?

A quantum cloud server like from IBM typically returns a string of 0's and 1's such as 0010. How is this measurement done exactly? I realize that the IBM cloud computers are transmon devices based on ...
Sam's user avatar
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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-...
LearnerAL's user avatar
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210 views

How to design a RF-SQUID qubit by Qiskit Metal?

I am now learning how to use Qiskit Metal to design superconducting circuits. I found that there are only several transmon qubits in the library. Can I design an RF-SQUID qubit by using Qiskit metal? ...
qcnewbie23's user avatar
4 votes
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What type of tasks it is possible to solve on a quantum simulator?

In this article, the author claimed that researches from Harvard and MIT created 256 qubits quantum simulator. However, we are not talking about piece of software on a classical computer but actual ...
Martin Vesely's user avatar
4 votes
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What is an electro-optic switch?

I found an implementation of a CNOT in photonic QC and I just couldn't find any info on a component named "electro-optic switch" What does it do exactly? How does it work? The ...
Mimo Pakou's user avatar
4 votes
0 answers
88 views

Clean way of approximating an oscillator by a qubit

Let me consider a (quantum) Harmonic oscillator of (bare) Hamiltonian: $$H_0=\frac{p^2}{2m}+\frac{1}{2} m \omega^2 x^2$$ (I can add to it an anharmonicity $V=\alpha x^4$ if necessary for the purpose ...
Marco Fellous-Asiani's user avatar
4 votes
0 answers
54 views

How to do the counting when computing the fault tolerant threshold of quantum codes?

Here, I want to ask a basic question about how to compute the fault tolerance threshold of quantum codes. As I know, maybe, the most usual way is to do some simulations. Howvever, I am more intersted ...
Bruce Fang's user avatar
4 votes
0 answers
106 views

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 ...
Dr. T. Q. Bit's user avatar
4 votes
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138 views

Form and effect of the intrinsic Hamiltonian on the IBM machines

I want to understand the form of the intrinsic Hamiltonian of the IBM machines, such as ibmq_16_melbourne, and how this affects the data I get out when waiting ...
Oscar Emil Sommer's user avatar
4 votes
0 answers
58 views

Is generating usable entanglement difficult?

I'm a theorist and I assume that I can use entanglement resources for practical use freely, but is this really the case? Is generating entanglement and storing it for long enough periods of time such ...
Stephen Diadamo's user avatar
4 votes
0 answers
237 views

What is the charging energy in relation to a superconducting transmon?

The transmon achieves its reduced sensitivity to charge noise by significantly increasing the ratio of the Josephson energy to the charging energy. What is this charging energy?
Logan's user avatar
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100 views

Individual processing of quantum circuit measurment results

When superconducting transmon qubits are measured with a readout pulse, the raw readout signal is demodulated, and results appear as clouds on the IQ plane, with one point in the cloud representing ...
psitae's user avatar
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3 votes
0 answers
151 views

What does the $\sigma_z$ operator correspond to in the context of a Transmon qubit?

In the context of the transmon qubit and an LC circuit with a coupling capacitor and driving voltage. We can write the charge operator $Q$ as $-iQ_{ZPF}\sigma_y$ (since we defined $Q$ using the ladder ...
bubakazouba's user avatar
3 votes
0 answers
84 views

Calculate Outputs of a Teleportation Circuit

In this question, I assume we use matrix representation to calculate what each output could be? For example, for the middle qubit in state: $$|00\rangle$$ After the first Hadamard and CNOT gate (so ...
Dwye's user avatar
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3 votes
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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 ...
v_enushk's user avatar
3 votes
0 answers
65 views

Are there any detailed designs for Quantum Computing hardware?

I am looking to analyze some quantum hardware designs, preferably superconducting and photonics, but I can't seem to find sources that give some detailed information. Can someone provide me designs ...
abhobe's user avatar
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3 votes
0 answers
63 views

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. ...
NNN's user avatar
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What is the difference between a cooper pair box and a transmon qubit?

These two kinds of qubits are both classified under "charge qubits", looking for them, I always find the same circuit representation. Occasionally, I find one where there's a SQUID instead of the ...
user2723984's user avatar
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3 votes
0 answers
54 views

Excitation of a superconducting circuit

What do we mean by exciting a superconducting circuit--which represent a qubit, how they are get excited inside? how the two states of the qubit are represented in this circuit?
walid's user avatar
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3 votes
0 answers
43 views

How to perform quantum logic gates on plasmons?

In the link provided researches utilize strong two-plasmon absorption in graphene nanoribbons to create a “square-root-of-swap”, could such a device be utilized to perform other quantum logic gates? ...
Marko Miloradovic's user avatar
3 votes
0 answers
98 views

States of a qubit in a DC-SQUID

Does anybody of you know what are the two states $|0\rangle$ and $|1\rangle$ of a qubit in a DC-SQUID (2 Josephson junctions in a loop)?
user1319236's user avatar
3 votes
0 answers
46 views

How much power do quantum computers use based on the number of qubits being allocated?

How much power do quantum computers use based on the number of qubits being allocated? If it's not based on qubits, What determines how much power quantum computers use? Note: A similar question was ...
AJ_4real's user avatar
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3 votes
0 answers
35 views

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?
Tejas Shetty's user avatar
3 votes
0 answers
51 views

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 ...
Tech Solver's user avatar
3 votes
0 answers
77 views

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 ...
Paul B. Slater's user avatar
3 votes
0 answers
61 views

Does self-induced collapse limit the size of a quantum computer?

This question is related to this question, but I'm specifically interested in self-induced collapse. Suppose that the size of a quantum system alone somehow leads to a projection of the state (a "...
M. Stern's user avatar
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2 votes
0 answers
91 views

Superconducting charge qubit and Cooper pairs

In the superconducting charge qubit implementation of the qubit what I've understood is that we read a 1 if a Cooper pair has gone through the Josephson Junction into the "island" and we ...
Omeglac's user avatar
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References discussing the carbon footprint expected for fault-tolerant quantum computers?

There are many problems regarding the scalability of quantum computers, how we need good quantum error correcting codes that scale well and protect well the logical encodings against many possible ...
R.W's user avatar
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2 votes
0 answers
43 views

The world's first quantum integrated circuit at the atomic scale - How does this advance quantum computing as a whole?

I have a hobbyist/enthusiast understanding of Quantum Computing, having read a few books on the subject. I came across this new article and referenced Nature paper. I know a goal of quantum computing ...
user2521987's user avatar
2 votes
0 answers
35 views

The energy levels crossover problem in Quantum Annealing

How to avoid energy levels crossover in quantum annealing by Kibble-Zurek mechanism? Any detailed references?
finely's user avatar
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2 votes
1 answer
399 views

How do I stepwise rotate a qubit on a Bloch sphere using $SO(3)$ and $SU(2)$ group?

Let us first introduce two fundamental functions for coordinate transformations: ...
Eldar Sultanow's user avatar
2 votes
0 answers
29 views

Experience on analog chaos based qc?

Any expirience on applied analog qc using a chaos based approach. By chaos I mean using analog components in chaos state thus changing between a wide range of states simultanously. The initial work on ...
Frank Schliephacke's user avatar
2 votes
0 answers
183 views

What is the dipole moment of a typical transmon qubit?

What is the dipole moment of a typical transmon qubit? I know this depends on the specific size, and that that varies from design to design. So let me provide an example situation: So given this size ...
psitae's user avatar
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2 votes
0 answers
33 views

What are the most popular QND measurement implementations used in photonic quantum computers?

What components are used in order to perform QND measurement in photonic quantum computers?
Mimo Pakou's user avatar
2 votes
0 answers
56 views

Crosstalk error of simultaneous cnots

We can use simultaneous randomized benchmarking (SRB) to quantify the crosstalk impact of simultaneous CNOTs. The crosstalk error is caused by many reasons, for example, the always-on ZZ interaction, ...
peachnuts's user avatar
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2 votes
0 answers
56 views

What are Sideband Pulses

I see sideband pulses used all over the place when looking up implementation techniques especially in Trapped Ion QC. Is there a layman's explanation of what they actually are? I understand what they ...
Bertrand Einstein IV's user avatar
2 votes
0 answers
28 views

What are the practical limitations of complementing quantum computations with memristors?

Considering the current state of research into quantum memristors, and the advantages/disadvantages of quantum and memristor driven computing architectures: Quantum Memristors Quantum Memristor ...
bey's user avatar
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