Data can be securely transmitted and manipulated infinitely faster with quantum computers and communication devices than with conventional electronics. The door to even faster and more powerful quantum communication tools has been opened by quantum researchers at Stevens Institute of Technology.
Quantum communication systems write information onto a photon. The two-dimensional qubit is formed by either a right or left circular rotation of the photon.
It's possible to put information onto a photon's corkscrew path, with each photon circling the center of the beam. A high-dimensional qudit can be formed when the spin and momentum interlock.
Flying qubits and flying qudits are used to transfer information between points. The foundation for next generation quantum communication can be found in the fact that qudits can carry more information over the same distance.
In a cover story in the August 2022, issue of Optica, researchers show that they can make and control individual flying qudits, or "twisty" photons, on demand.
There are two properties of a photon that are not dependent on one another. The device is the first to demonstrate simultaneous control of both properties, thanks to the work of Yichen Ma, a graduate student at the University of Pennsylvania, and Jim Hone, a professor at the University of Pennsylvania.
It's a big deal because we've shown we can do this with single photons instead of classical light beams, which is the basic requirement for any kind of quantum communication application.
The information that can be transmitted is greatly increased by Encoding it. Enhancing the bandwidth of quantum communication tools would allow them to transmit data much faster.
The team used an atom-thick film of tungsten diselenide to create a quantum emitter that could emit a single photon.
They put the quantum emitter in a ring resonator. By fine- tuning the arrangement of the emitter and the gear-shaped resonator, it's possible to leverage the interaction between the photon's spin and its angular momentum.
When carefully engineered in the design, the gear-shaped patterning of the ring resonator creates a light beam that shoots out at the speed of light.
The team was able to integrate those capabilities into a single chip measuring just 20 microns across, which is about a quarter of the size of a human hair.
Key challenges still exist. The team's technology is able to control the direction in which a photon spirals, but more work needs to be done to control the exact number. That is the critical capability that will allow a theoretically infinite range of different values to be written into and later extract from a single photon. Ma said that the latest experiments show that the problem can be solved.
A key requirement to enable the quantum internet is the creation of a device that can create twisted photons with consistent quantum properties. Ma said that the challenges affect everyone working in the field.
He said there were a lot of challenges ahead. We have shown that quantum light sources can be more versatile than before.
More information: Yichen Ma et al, On-chip spin-orbit locking of quantum emitters in 2D materials for chiral emission, Optica (2022). DOI: 10.1364/OPTICA.463481 Journal information: Optica
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