All Questions
Tagged with quantum-computer quantum-optics
30 questions
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How to transform collapse operators in rotating frame?
I want to simulate the evolution of a transmon qubit driven by a classical voltage using qutip. The problem is that the qubit (and the drive) have a frequency of around 5GHz and I typically run ...
- 1,150
1
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146
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Using classical $g^{(1)}$ to calculate quantum $g^{(1)}$
Imagine a free space optical switch with several inputs and outputs. My question is: can we use the first order cross correlation between the complex amplitudes of two classical beams of light at the ...
- 11
1
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34
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Photonic classical and quantum computing
How different is the hardware used for classical and quantum photonic computers? Are there any proposals on hybrid platforms? I'm curious why I never heard of both within the same context, except for ...
- 3,013
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2
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Why does the Lamb-Dicke parameter decrease with the number of ions in an ion chain
I would like to understand (ideally with a nice pedagogic reference), why the fidelity of quantum gates in long ion chain decreases with the number of ions in the chain.
In this reference, it is ...
- 1,560
2
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1
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142
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How can the Rabi frequency be complex?
I've been doing some reading and came across a simple implementation of the Hadamard gate using Rabi oscillations of an atom in a laser field. However, the author mentions that it required the Rabi ...
- 45
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98
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Josephson supercurrent measurement in a lab
This may be a very trivial question but I am a theoretician and can't find the answer to this question for the life of me. Is it possible to actually measure the Josephson supercurrent flowing through ...
- 155
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1
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44
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What guarantees a photonic quantum gate to be unitary?
So in my course of quantum computation i came across this question that "What guarantees a quantum gate to be unitary?" i was specially curious about photonic quantum gate.
At first i ...
1
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1
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93
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How can beamsplitters and measurements be used to make a quantum cNOT gate?
It's possible to create a two-photon gate using detectors and linear optics, which can be used as the basis for a quantum computer.
I am struggling to get a basic understanding of how this works. I'm ...
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32
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How can one compute the quantum motion of an ion in a trapped ion quantum computer?
I am trying to get a conceptual idea of a trapped ion quantum computer.
For simplicity, I am looking at a single ion in a Paul ion trap.
It is easy enough to define the potential of the ion trap and ...
1
vote
1
answer
82
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Wavelength-dependence of optical elements in integrated photonic circuits
I am interested in integrated photonic circuits or silicon photonic circuits. In the long run, I would like to analyze these circuits using a rigorous and analytical mathematical approach, taking the ...
- 514
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35
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What optical elements can you use to implement an S gate in practice?
How do you implement an S gate using an optical element or combination of optical elements in the following 2 scenarios?
The S gate acts on a polarization qubit (polarization of a photon)
The S gate ...
- 362
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124
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Why/how does Microwave pulse cause electron spin to rotate in the Bloch sphere?
I recently started studying pulse techniques for electrons in the context of quantum computing/sensing/optics/etc.
For spins in solid state (like color centers in diamond or SiC, or metal centers in ...
- 11
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1
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63
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Displacement gate on an arbitrary quantum state
I am reading this reference. In this article, the author define the Heisenberg-Weyl operators (Eqs. [148] in the reference):
$$X(s)=e^{-is\hat{p}/2} \tag{1},$$
$$Z(t)=e^{it\hat{q}/2} \tag{2},$$
where $...
0
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1
answer
122
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What optical element can you use to implement a square root of NOT gate
How do you implement a square root of NOT gate in an optical quantum computing circuit? What optical element or combination of elements would you use - especially, if you want to manipulate ...
- 362
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0
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80
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What are Sideband Pulses?
I asked this question on Quantum Computing SE about a month ago and haven't gotten any answers https://quantumcomputing.stackexchange.com/questions/15646/what-are-sideband-pulses. Was hoping someone ...
- 1,806
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212
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Is there a way to go from the continuous variable quantum computer model to the qubit model?
There are some papers such as https://arxiv.org/abs/quant-ph/0008040 and https://arxiv.org/abs/1907.09832 that discuss going from qubit to the continuous model. But I'm curious if there is a way to ...
- 251
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1
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512
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Applying a rotation on an entangled state
I want to understand an experiment but I am struggling with the (basic) math/braket notation.
In the experiment two ions are entangled and separated into two wells $A$ and $B$. The spin state of the ...
2
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0
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116
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What are current open questions in quantum measurement research? [closed]
Here we go, another question about quantum measurement... but bear with me.
When asking about quantum measurement one inevitably runs into discussions of various interpretations of quantum theory, ...
- 11.7k
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1
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337
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Why isn’t light polarization used as a physical realization of a quantum computer?
Constructing a qubit requires something that can be represented as a linear combination of two states. The physical realizations are numerous
https://en.wikipedia.org/wiki/Quantum_computing
But I do ...
- 1,729
-1
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1
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170
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Inverse covariance matrix for a Gaussian state
I was reading an article about Gaussian Boson Sampling (https://arxiv.org/pdf/1801.07488.pdf) and following some calculation appear an inverse covariance matrix when he defines the following matrix A.
...
0
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1
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109
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Why is EIT needed to story memory using rydberg atoms?
I was going through a paper explaining how the write-in and read-out efficiencies can be increased using cold atoms where they used Rydberg atoms, and mentioned that they were probed using EIT(...
- 581
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2
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782
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Are photons being considered as qubits for a potential quantum computer?
I've been reading a few articles on photons that are capable of carry bits of information. I was wondering if anyone knew if there are any team of research scientist who have tried to use a photon as ...
- 107
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1
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225
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Is the DC/electro-optical Kerr effect usable in optical quantum computing?
It seems from @EmilioPisanty's comments on this question that the AC/optical Kerr effect is impractical for use in optical quantum computers, which leads me to ask: would the DC Kerr effect work?
The ...
- 7,087
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1
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435
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Meaning of "intensity" in the optical Kerr effect in optical quantum computation
Kerr media, or mediums displaying the optical Kerr effect, are used in some optical quantum computers - on Chuang and Nielsen's Quantum Computing and Quantum Information, pgs. 289 - 290, it says,
...
- 7,087
9
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1
answer
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Output of a beamsplitter with photon number (Fock) state inputs
Given a beamsplitter drawn below, where $\hat{a}$ and $\hat{b}$ are input modal annihilation operators, transmissivity is $\tau\in[0,1]$, and output modal annihilation operators are $\hat{c}=\sqrt{\...
- 251
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1
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195
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What is three-photon interference?
Whilst reading this paper on a quantum processor that performs a type of matrix computation, I came across the concept of 'three-photon interference'. A quick Google search shows that this process is ...
- 235
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1
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123
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Using wavepackets instead of photons in quantum computer
Why does a photonic quantum computer require photons? Why wouldn't wave packets work just as well, better in fact since it would get away from the use of fragile single photons? (Article)
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246
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Quantum Cryptography
First question was a little bit ambiguous.
Photons are passed through a linear polarizer that is oriented $\theta$ degrees again the photon passes through another linear polarizer that also have a $\...
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3
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7k
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Quantum memories: What are they?
Searching the literature for the term "quantum memory" seems to bring up results from two different communities.
On the one hand there are quantum opticians, who see a quantum memory as something ...
- 695
11
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412
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Which qubit states are accessible with linear optics operations?
Given a quantum state of $n$ qubits, and being restricted to linear optics (that is, the output annihilation operators are linear combinations of the input annihilation operators):
Which states are ...
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