Twisted photons could charge next-generation quantum communications

Usually, the information is “written” to the photon’s spin angular momentum in quantum communication systems. In this scenario, the photons either spin left or right or combine to produce 2D qubit, a quantum superposition of the two. The information can also be stored on the photon’s orbital angular momentum, taking the light of the key’s path as it advances as each photon orbits around the center of the beam.

Qubits and qudits spread the information stored in photons from one point to another. The main difference is that qubits can carry much more information over the same distance than qubits, providing the basis for next-generation turbocharging. quantitative communication.

In a new study, quantum scientists in Stevens Institute of Technology They demonstrated a way to encode more information into a single photon, opening the door to faster and more powerful quantum communication tools. It also shows that they can create and control individual flight units or “twisted” photons on demand.

Yichen Ma, a graduate student in Strauf’s NanoPhotonics lab, said, Normally, spin angular momentum and orbital angular momentum are independent properties of a photon. Our device is the first to demonstrate simultaneous control of both properties through the controlled coupling of the two. We’ve shown that we can do this using single photons instead of classical beams of light, which is a basic requirement for any quantum communication application.”

“Encoding information into orbital angular momentum drastically increases the information that can be transmitted. Taking advantage of “twisted” photons could boost the bandwidth of quantum communication tools, enabling them to transmit data much more quickly.”

The scientists used an atom-thick film of tungsten diselenide to create twisted photons to create a quantum emitter capable of emitting single photons. Next, they wired the quantum emitter into an internally reflective, doughnut-shaped space called a circular resonator. By adjusting the arrangement of the emitter and the resonator to the shape of a gear, it is possible to take advantage of the interaction between a photon’s spin and its orbital angular momentum to create individual “twisted” photons on demand.

This rotary momentum lock function enable switch relies on the gear-shaped decoration of the annular resonator, which, when carefully engineered into the design, creates a twisting vortex beam of light that the device emits in light’s speed.

By incorporating these capabilities into a single microchip that is only 20 microns wide—about a quarter of the width of a human hair The team has created a twisted photon emitter capable of interacting with other modular components as part of a quantum communication system.

ma He saidAnd the “Some key challenges remain. While the team’s technique can control the direction in which a helical photon is – clockwise or counterclockwise – more work is needed to control the exact orbital angular momentum mode number. This critical capability will enable from “writing” a theoretically infinite range of different values ​​and subsequently extracting them from a single photon. Recent experiments at the Struve Nanophotonics Laboratory show promising results that this problem can soon be overcome.”

“More work is also needed to create a device that can create twisted photons with strictly consistent quantum properties, that is, indistinguishable photons – a key requirement to enable As far as the Internet. Such challenges affect everyone working in quantum photonics and may require breakthroughs in materials science to solve them.”

“Lots of challenges lie ahead. But we have shown the possibility of creating quantum light sources more diverse than anything previously possible.”

Journal reference:

  1. Yichen Ma et al. , On-chip spin-orbit locking for quantum emitters in 2D materials for chiral emission, Visual (2022). DOI: 10.1364 / OPTICA.463481