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Quantum Superradiance

dramatic quantum leap: superradiance 17-folds the entanglement range, enabling scalable quantum technology

An international team of researchers made a theoretical breakthrough that could revolutionise quantum sensing, secure telecommunications, and quantum computing. Scientists created a photonic chip that uses long-range quantum superradiance in materials with near-zero refractive indices to extend quantum entanglement between emitters 17 times farther than in a vacuum. This is a crucial step towards scalable, practical quantum technologies.

MTU, Harvard, Sparrow Quantum, and Namur researchers worked on the project. The prestigious journal Light: Science & Applications describes their innovative dielectric photonic chip, which solves some of the biggest quantum entanglement issues across distance.

Near-Zero Index Materials Unlock Long-Range Superradiance

In 1954, Robert Dicke mathematically theorised superradiance, a physical phenomenon known for almost 50 years. Superradiance occurs when atoms or other elements synchronise to create a stronger light, like a chorus singing louder than individual voices. This effect usually requires close emitters.

The emitter environment is the game-changer, according to these experts. They can avoid the distance requirement for superradiance by submerging in a near-zero refractive index medium. Refractive index describes light's action in a material. Light behaves in a near-zero index medium as if the “sea becomes perfectly flat, with no waves,” moving in unison and extending eternally. Due to this consistency, all atoms are optically close even when physically separated, relaxing a key quantum entanglement requirement.

Professor Michaël Lobet of the University of Namur said that superradiance in media with near-zero refractive index has been a significant research issue for the past decade. Professor Eric Mazur of Harvard School of Engineering and Applied Sciences stated this discovery shows how near-zero refractive index photonics can connect classical electrodynamics with quantum superradiance.

Unprecedented Entanglement Range Photonic Chip

Dr. Larissa Vertchenko from Sparrow Quantum led the research team, which included Adrien Debacq from UNamur, to hypothetically develop a photonic chip that greatly expands entanglement. They use quantum optics-renowned nitrogen vacancy (NV) diamond emitters in their model.

The theoretical model predicts a 12.5-micrometre entanglement range, 17 times greater than a vacuum. “This is the first time such a long range has been achieved using a compact system that is easily implementable in photonic chips,” Professor Lobet said. This range increase greatly improves earlier works limited by small distances and significant loss.

The mechanism has three steps:

The dielectric mu-near-zero (μNZ) metamaterial extends light wavelengths by generating an environment with a near-zero refractive index.

This longer wavelength strengthens the photonic chip-quantum emitter interaction with NV diamonds.

The system can maintain entanglement across longer distances, possibly exceeding 17 free-space wavelengths due to superradiance in this stretched wavelength environment.

This new approach uses a dielectric platform instead of lossy plasmonic materials, making it feasible and lossless. Dielectric materials are ideal for scalable quantum technologies because they reduce energy dissipation and work better with on-chip NV diamond technology.

Transformative Applications Ahead

Broad implications of this discovery could accelerate the “second quantum revolution”:

Long-range entanglement is needed to build scalable quantum computers that can perform more complex and dependable quantum operations. According to Dr. Durdu Güney of MTU, multipartite entanglement involving many qubits may result from maintaining a high degree of entanglement over longer distances to create cluster states needed for large-area distributed quantum computing and universal one-way quantum computing.

Secure Communications: Extended entanglement may enable more durable and secure quantum communication networks by increasing channel capacity. This technique could revolutionise cybersecurity by securing messages with physical rules rather than complex algorithms.

Advanced Sensing: The technique may enable more sensitive and precise optical sensors.

From Theory to Experiment

Even while theoretical models and numerical simulations are appealing, implementing this concept experimentally is the next challenge. The ultimate goal is to create usable quantum systems as small as a hair. Researchers plan to carry quantum computers in pockets one day.

The research was made possible by the Department of Physics, NISM Institute, FNRS for Michaël Lobet and Adrien Debacq, and PTCI technology platform, whose supercomputers were essential. The U.S. Army Research Office supplied some cash through a MURI award.