Single-photon source paves the way for practical quantum encryption
New source is compact and operates at room temperature

Date:
March 23, 2022
Source:
Optica
Summary:
Researchers describe new high-purity single-photon source that
can operate at room temperature. The source is an important step
toward practical applications of quantum technology, such as highly
secure communication based on quantum key distribution (QKD).



FULL STORY ========================================================================== Researchers have developed a new high-purity single-photon source that
can operate at room temperature. The source is an important step toward practical applications of quantum technology, such as highly secure communication based on quantum key distribution (QKD).


==========================================================================
"We developed an on-demand way to generate photons with high purity
in a scalable and portable system that operates at room temperature,"
said Helen Zeng, a member of the research team from the University of Technology Sydney in Australia. "Our single-photon source could advance
the development of practical QKD systems and can be integrated into a
variety of real-world quantum photonic applications." In the Optica
Publishing Group journal Optics Letters, Zeng and colleagues from
Australia's University of New South Wales and Macquarie University
describe their new single-photon source and show that it can produce
over ten million single photons per second at room temperature. They
also incorporated the single-photon source into a fully portable device
that can perform QKD.

The new single-photon source uniquely combines a 2D material called
hexagonal boron nitride with an optical component known as a hemispherical solid immersion lens, which increases the source's efficiency by a factor
of six.

Single photons at room temperature QKD offers impenetrable encryption
for data communication by using the quantum properties of light to
generate secure random keys for encrypting and decrypting data. QKD
systems require robust and bright sources that emit light as a string
of single photons. However, most of today's single-photon sources don't
perform well unless operated at cryogenic temperatures hundreds of
degrees below zero, which limits their practicality.



========================================================================== Although hexagonal boron nitride has previously been used to create
a single- photon source that operates at room temperature, until now researchers had not been able to achieve the efficiency needed for
real-world application. "Most approaches used to improve hexagonal boron nitride single-photon sources rely on precisely positioning the emitter
or using nano-fabrication," said Zeng.

"This makes the devices complex, difficult to scale and not easy to
mass produce." Zeng and colleagues set out to create a better solution
by using a solid immersion lens to focus the photons coming from the single-photon emitter, allowing more photons to be detected. These lenses
are commercially available and easy to fabricate.

The researchers combined their new single-photon source with a
custom-built portable confocal microscope that can measure the single
photons at room temperature, creating a system that can perform QKD. The single-photon source and confocal microscope are housed inside a robust
package that measures just 500 x 500 millimeters and weighs around 10 kilograms. The package is also engineered to deal with vibration and
stray light.

"Our streamlined device is easier to use and much smaller than
traditional optical table setups, which often take up entire labs,"
said Zeng. "This allows the system to be used with a range of quantum
computing schemes. It could also be adapted to work with existing telecommunications infrastructure." Demonstrating quantum cryptography
Tests of the new single-photon source showed that it could achieve a
single- photon collection rate of 107 Hz while maintaining excellent
purity -- meaning each pulse had a low probability of containing
more than one photon. It also showed exceptional stability over many
hours of continuous operation. The researchers also demonstrated the
system's ability to perform QKD under realistic conditions, showing
that secured QKD with 20 MHz repetition rates would be feasible over
several kilometers.

Now that the researchers have established proof that their portable
device can perform complex quantum cryptography, they plan to perform
further testing of its robustness, stability, and efficiency during
encryption. They also plan to use the new source to perform QKD in
real-world conditions, rather than inside the lab. "We are now ready
to transform these scientific advances in quantum 2D materials into
technology ready products," said Igor Aharonovich, who led the project.


========================================================================== Story Source: Materials provided by Optica. Note: Content may be edited
for style and length.


========================================================================== Related Multimedia:
* A_new_high-purity_single_photon_source ========================================================================== Journal Reference:
1. Helen Zhi Jie Zeng, Minh Anh Phan Ngyuen, Xiaoyu Ai, Adam Bennet,
Alexander S. Solnstev, Arne Laucht, Ali Al-Juboori, Milos Toth,
Richard P. Mildren, Robert Malaney, Igor Aharonovich. Integrated
room temperature single-photon source for quantum key
distribution. Optics Letters, 2022; 47 (7): 1673 DOI:
10.1364/OL.454450 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220323125124.htm

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