This document discusses quantum photonics and its applications. It begins by outlining the importance of quantum photonics in fields like information processing, communication, measurement, and nanotechnology. It then provides an introduction to basic photonics concepts like photons, quantum states, and coherence. The document outlines several applications of quantum photonics in areas like quantum information processing, quantum metrology, quantum teleportation, and quantum cryptography. It also discusses advantages like secure communication and accurate measurements. Future challenges are identified as developing quantum computers, multi-particle teleportation, and a quantum internet. The document concludes by noting that quantum photonics will continue to play a central role in future technologies.

1. By,
HIMANSHU BANSAL
M.Sc. IInd sem.
155274

2. OUTLINES
Importance of topic
Introduction & Basic principle
Applications
Advantages
Future challenges
conclusion

3. Importance of topic
This is a broad research field which have made a lot
of researches in many areas, some area are listed
below…….
Information processing and communication
measurement
 data security
 computing
Nano technology
 Teleportation
And still there is a lot of research work is going on …..

4. 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 photonics
In 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).

5. 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

6. 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.

7. 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’.

8. 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?

9. 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.

10. 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

11.  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

12. 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
Application

13. 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

14. Quantum lithography
Quantum 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
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.

15. And there are more various applications…..
 Integrated quantum optical circuits
 Detectors based on quantum
phenomena
 Quantum computing
 Optical quantum memory,
etc.
Application

16. Advantages
Transmission 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.

17. 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.

18. 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

19. 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.

20. Future challenges
Quantum computer
Multi-particle teleportation
 quantum communications
 quantum Metrologic strategies
Optical quantum memory
 quantum internet

21. conclusion
We 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.

22. References
NATURE PHOTONICS /VOL 3/ DEC.
2009/www.nature.com/naturephotonics
Nielsen, 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-here
12 March 2011 / Accepted: 2 June 2011 / Published online: 16
June 2011 © Springer Science+Business Media, LLC 2011

23. Thank you

24. Any query