Quantum Computing Stack Exchange
Quantum Computing Stack Exchange

Questions tagged [optical-quantum-computing]

For questions about the specific realization of quantum computing that uses photons as qubits. Examples of gates include the Fabry-Perot cavity or linear optical components like beamsplitters. Questions with this tag can ask about both theory and practice, as long as it relates to this specific realization.

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Why do optical quantum computers not have to be kept near absolute zero while superconducting quantum computers do?

This is a follow-up question to @heather's answer to the question : Why must quantum computers be kept near absolute zero? What I know: Superconducting quantum computing: It is an implementation of a quantum computer in a superconducting electronic…
Sanchayan Dutta
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Is it possible to "calculate" the absolute value of a permanent using Boson Sampling?

In boson sampling, if we start with 1 photon in each of the first $M$ modes of an interferometer, the probability of detecting 1 photon in each output mode is: $|\textrm{Perm}(A)|^2$, where the columns and rows of $A$ are the first $M$ columns of…
user1271772 No more free time
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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 optical quantum computing (LOQC)" pioneered by KLM…
rrtucci
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State produced by spontaneous parametric down-conversion (SPDC)

I'm researching SPDC's efficacy for use in an optical quantum computing model and I've been trying to figure out exactly what state the photons are in when they come out (as represented by a vector, for example), if I'm using type 1 SPDC and I'm…
auden
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What is the status of quantum computing compared with other (photonic) quantum technologies?

There is a number of emerging quantum technologies, among which we find the category of photon-based quantum technologies, including quantum key distribution or quantum random number generators. The question is: what is the short-term viability of…
agaitaarino
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How do you apply a CNOT on polarization qubits?

I read that a qubit can be encoded in a polarization state (horizontal or vertical polarization of a photon). How do you perform two-qubit operations on a polarization qubit?
Daniel Tordera
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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 temperature (for superconducting to happen), or vacuum…
Aleksandar Kostovic
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Improving probability of spontaneous parametric down conversion

As mentioned in an earlier question of mine, I am interested in using type one spontaneous down conversion (SPDC) in optical quantum computing. However, SPDC is a somewhat low probability occurrence - most of the photons pass straight through the…
auden
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What are some good resources for learning about photonic qubits?

I am interested in resources that would allow me to learn about the physics behind optical quantum computation, and specifically, the physical properties of photonic qubits. I have some good resources on quantum optics, but is there anything more…
Jack Ceroni
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Shor's Code: Understanding how it satisfies Knill Laflamme Theorem

I'm new to Quantum Error Correction, and I have a question on Shor's Code. If we have a protected subspace, $V \subset \mathbf{C}^2\otimes \cdots \otimes \mathbf{C}^2$ $V=\operatorname{span}\{|0_{l}\rangle, |1_{L}\rangle.$ We also consider Pauli…
Anon
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Physical qubit of optical quantum computer

I was researching how optical quantum computers work and discovered a KLM protocol that allows for building quantum gates using linear optics elements like mirrors, beam splitters, and phase shifters. However, I was wondering how would we get the…
Aleksandar Kostovic
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Does a photonic quantum computer control a single photon?

Does a photonic quantum computer control a single photon and use it to represent a single qubit? I think ion trapped quantum computers use a single ion to represent a qubit. I would like to know how a photonic quantum computer represents each qubit.
david
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What is the relation between single photon qubits and squeezed light qubits?

In my constant thrill to know more about Quantum Computing I wanna know what is this relation. Additionally: Can one use squeezed light to effect multi-qubit operations on single photon qubits, or are these completely independent approaches?
Daniel Tordera
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Multi-photon states in photonic quantum computing?

Within photonic quantum computing, one of the ways to represent information is the dual-rail representation of single-photon states ($c_0|01\rangle \ + \ c_1|10\rangle$). Is it possible to utilize multi-photon states (for example, two optical…
Jack Ceroni
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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 blueprints or schematics for working photonic gates.
Spock
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