By, HIMANSHU BANSAL

M.Sc. IInd sem.155274

OUTLINESImportance of topicIntroduction & Basic principleApplicationsAdvantagesFuture challengesconclusion

Importance of topicThis is a broad research field which have made

a lot of researches in many areas, some area are listed below…….

Information processing and communicationmeasurement data security computingNano technology Teleportation

And still there is a lot of research work is going on …..

INTRODUCTION PHOTONICS

PHOTON ELECTRONICS“PHOTOICS” comes from PHOTON , which is the

smallest unit of light just as an ELECTRON is the smallest unit of electricity.

PHOTONICS is the generation, process and manipulation of photon to achieve a certain function.

Quantum photonicsIn quantum phonics, we study quantum and coherent

properties of light and it’s applications.In this area, The research group is focusing on

developing techniques to control the quantum dynamic of a single quantum of light (a photon), which interacts with a single quantum of matter (an atom).

There are various principles referring to application we will discuss later but the most required property, which is used, is quantum state of the PHOTON and it’s coherence.

PHOTON have two polarized state, which may be horizontal represented by |H or vertical ⟩represented by |V⟩ .

Basic principle

A qubit — a quantum ‘bit’ of information , can be encoded using the horizontal (|H ) and ⟩vertical (|V ) polarization of a single photon.⟩

And magic is that it can be in both states at same time which we called superposed state (before measurement)

Also property of Quantum entanglement of photons are used in some applications.

Here we provide a broad review of photonics for quantum technologies touching on topics including secure communication with photons, quantum information processing, quantum lithography and integrated quantum photonics.

Application As I told before, there are various fields in which

quantum photonics have made remarkable success…Some of them are listed below.Quantum information processing(QIP)-: The requirements for realizing a quantum computer

are conflicting till now. A major difficulty for optical QIP is the realization of two qubit entangling logic gates.

The canonical example is the controlled-NOT (CNOT) gate, which flips the state of a target qubit only if the control qubit is in the state ‘1’.

It will makes is too faster.

Quantum metrology -: All science and technology is

founded on measurement. And improvements in precision have led not only to more detailed knowledge but also to new fundamental understanding. The quest to realize increasingly precise measurements raises the question of whether fundamental limits exist or not?

e.g.- Interferometers have found application in many fields of science and technology, from cosmology (gravity-wave detection) to nanotechnology (phase-contrast microscopy) , because of the subwavelength precision they offer for measuring an optical phase φ.

However, the phase sensitivity is limited by statistical uncertainty, for finite resources such as energy or number of photons, It has been shown that using semi-classical probes (coherent laser light, for example) limits the sensitivity of Δφ to the standard quantum limit (SQL) such that Δφ ∼ 1/√N, where N is the average number of photons used. But now, The more fundamental Heisenberg limit is attainable with the use of a quantum probe (an entangled state of photons, for example) such that Δφ ∼ 1/N — this is referred to as quantum metrology.

Quantum teleportation-: in this process , we use the entangled

state of photons, which was shared between the sending and receiving point.

till now, we have teleported single photons at few hundred miles , but still it is impossible to teleport a system containing few thousands atoms, as we required. ( but physicist say “not impossible, but very very hard”).

Application

semiconductor-based single-photon sources:

Many quantum technologies, including QKD (quantum key distribution) and photonic qubit based quantum computation and networking, require sources of single photons on demand. Ideally, such a source should have a high efficiency , a very small probability of emitting more than one photon per pulse, and should produce indistinguishable photons at its output. These above three parameters are critical for almost all QIP applications, although some QKD protocols.

Application

The basic idea used to generate single photons on demand is very simple: a single quantum emitter (such as a quantum dot, an atom, a molecule, a nitrogen vacancy centre in diamond or an impurity in a semiconductor) is excited with a pulsed source, after which spectral filtering is applied to isolate a single photon with the desired properties at the output.

The solid matter the researchers are working with are so called quantum dots, which are ‘artificial’ solid state atoms. Quantum dots consist of thousands of atoms embedded in nanophotonic structures, so called photonic crystals. In a photonic crystal, the interaction between a quantum dot and a single photon can be so powerful that quantum optical effects can be observed.

Application

Quantum cryptography-: Quantum cryptography is an emerging

technology in which two parties can make secure network communications by applying the phenomena of quantum physics.

Application

Quantum lithographyQuantum lithography is a technique that allows one

to write interference fringes with a spacing N-times smaller than the classical Rayleigh limit of resolution, which is approximately λ/2.

That is, if N photons are entangled and the recording medium responds by N-photon absorption, features of size λ/(2N) can be written into the material.

Application The appealing characteristic of quantum

cryptography is the possibility of distributing secret key between two users in a manner that it is impossible for a third party to eavesdrop without changing the quantum transmission and hence the eavesdropping is detected by users.

And there are more various applications…..

Integrated quantum optical circuits Detectors based on quantum

phenomena Quantum computing Optical quantum memory, etc.

Application

AdvantagesTransmission at the speed of light and low-noise

properties make photons extremely valuable for quantum communication — the transferring of a quantum state from one place to another

ability to transfer quantum states between remote locations can be used to greatly enhance communication security. Any measurement of a quantum system will disturb it, and we can use this fundamental fact to reliably detect the presence of an eavesdropper.

We can say, It’s allow more secure transmission of information, and perform more accurate measurements. 

It’s gives ,highly efficient detectors, integrated photonic circuits, and waveguide- or nanostructure-based nonlinear optical devices.

Quantum technologies will be able to implement faster algorithms or we can say faster computing.

In 2001, a surprising breakthrough showed that scalable quantum computing is possible simply by using single-photon sources and detectors, and linear optical networks; and also by using optical nonlinear properties.

Latest research work

In the latest work from the quantum photonics group at the University of Bristol, Jonathan Matthews and colleagues report the construction of a reconfigurable quantum optical circuit on a chip and the control of entangled states with up to four photons1. The heart of their device is a simple heating element that changes the phase in one arm of an interferometer.

Future challengesQuantum computerMulti-particle teleportation quantum communications  quantum Metrologic strategiesOptical quantum memory quantum internet

conclusionWe have just witnessed the birth of the first

quantum technology based on encoding information in light for quantum key distribution. The quantum nature of light seems destined to continue to have a central role in future technologies.

References NATURE PHOTONICS /VOL 3/ DEC.

2009/www.nature.com/naturephotonicsNielsen, M. A. & Chuang, I. L. Quantum Computation

and Quantum Information. (Cambridge Univ. Press, 2000).

Gisin, N. & Thew, R. Quantum communication. Nature Photon. 1, 165–171 (2007).

Peter Lodahl,* Sahand Mahmoodian, and Søren Stobbe Niels Bohr Institute, University of Copenhagen

https://www2.physics.ox.ac.uk/study-here12 March 2011 / Accepted: 2 June 2011 / Published

online: 16 June 2011 © Springer Science+Business Media, LLC 2011

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