1) A quantum router uses quantum entanglement to coherently route photons along different optical paths controlled by the polarization state of a control photon. 2) Researchers in China demonstrated the first working quantum router by entangling pairs of photons and using the polarization of one photon to determine the path of the other in a quantum superposition of routes. 3) Major challenges remain in scaling up quantum routers for use in a quantum internet, but China aims to have the first operational quantum internet within 5 years to take advantage of quantum communication capabilities far exceeding classical networks.

1. Quantum Router
Submitted by : Ms.Yojana
ME(CSE-I) : Roll No. - 01

2. Overview
• Definition
• Working of QR
• 1st
Demonstration of QR
• Research
• Challenge

3. Definition
• Quantum is a discrete quantity of energy
proportional in magnitude to the frequency of the
radiation it represents.
• It is an analogous discrete amount of any other
physical quantity, such as momentum or electric
charge.
• Router is a device which forwards data packets
to the appropriate parts of a computer network

4. Working of QR

5. Contd…
• Fig. (A) Illustration of a genuine quantum router. The
control photon can be in arbitrary superposition states
with coecients c0; c1 that determine the path of the
signal photon.
• Fig. (B) the entanglement-based approach to
implementation of a genuine quantum router. With a bit
of pre-shared entanglement, the quantum router can be
realized with linear optical devices.
• The control coecients c0; c1 are imprinted through
operation on the control photon alone with a polarization
rotator and alter. The routing is realized with a
polarization beam splitter (PBS) and a wave plate on the
signal photon.

6. Contd…
• An experiment that demonstrates full function of a
quantum router using entangled photons, where the
paths of a single-photon pulse are controlled in a
coherent fashion by polarization of another single
photon. Through a projective measurement, the
polarization of the control photon in arbitrary
superposition states, leading to coherent routing of the
target photon in quantum superposition of different
paths. Demonstrate quantum nature of this router
through optical measurements based on quantum state
tomography and show an average fidelity of $(93.24pm
0.23)%$ for the quantum routing operation.

7. 1st
Demonstration of QR

8. Contd..
• Chinese physicists unveil a router that uses a quantum
control signal to determine path of quantum data signal.
• Physicists have exploited the quantum nature of photons to
transmit information for some time now. And in doing so
they’ve discovered just how powerful quantum
communication can be compared to the classical kind.
• Instead of sending the 0s and 1s of digital code, quantum
communicators can send information in a superposition of
states that represent both 0s and 1s at the same time.
What’s more, separate quantum objects such as a pair of
photons can be entangled, which means they share the
same existence even if they are widely separated. That
leads to a form of quantum information that has no
classical counterpart.

9. Research in QR
• Physicists Demonstrate Working Quantum Router, a
Step Toward a Quantum Internet
• As we know silicon semiconductors, quantum computers
are very much a technology of the future. Instead of the
usual string of 1s and 0s, they'll be able to send both
types of information at the same time, dwarfing their
traditional counterparts. But one major problem is that
they can only move through one optical fibre. To push
more information through, they need a router.

10. Contd…
• In a quantum computer, photons ferry information to
other sources. It's possible to send the photons directly
through one fibre, but routing comes in when another
fibre is needed. Like the router you probably own, a
control signal reads the data then sends it to its
destination. But dealing with unruly quantum particles is
a little more complicated; when a signal is read it's also
destroyed. So even though the data can be transferred
with traditional methods, that doesn't offer the kind of
data-transferring power quantum computing offers.

11. Contd…
• This new quantum router proves it's possible to truly
guide a quantum signal. The information used is
encoded in two different types of polarized photons (like
1s and 0s). Scientists then create a single photon that
acts as both (the combined 1s and 0s). That photon is
then broken down into two photons that share the
combined state. The router picks up one to determine
the route, then the other photon is used to transfer the
information. A simple series of half mirrors guides the
photons along the correct route.

12. Challenge
• Now after successful working & demonstration of
Quantum Router partially by using theoretical
knowledge, China want to run Quantum Internet
in world gracefully within 5 years.