Squeezed Light: A Quantum Breakthrough by UA Researchers
In a quantum breakthrough, scientists use ultrafast squeezed light to control uncertainty.
Beginning of Ultrafast Quantum Optics
University of Arizona (UA) researchers have made major scientific advances with a global collaboration by using ultrafast light pulses to capture and govern quantum uncertainty in real time. It is the first ultrafast squeezed light demonstration and real-time quantum uncertainty measurement and control. This remarkable finding involves femtosecond “squeezed light” production and manipulation.
Understanding Quantum Uncertainty Taming
This invention relies on quantum physics' uncertainty management. Light is two qualities that approximate a particle's position and intensity. Importantly, these two traits cannot be accurately determined.
Quantum principles limit the product of these two measurements to a particular threshold, similar to a balloon's air volume.
Hassan compares ordinary light to a round balloon with similar error in its measurements. Stretching quantum light, or “squeezed light,” forms an oval. This setup makes the first property quieter and more accurate while the other property gets noisy.
For gravitational-wave detectors, compressed light reduces background noise and detects minuscule spacetime ripples from distant celestial entities.
Overcoming Femtosecond Pulse Technical Issues
Older compressed light uses required millisecond laser pulses. Hassan measured ultrafast pulses in femtoseconds to test compressed light.
Phase-matching different-colored lasers, which needs expensive equipment, was the biggest technological barrier. Hassan realized his team's technology could address this phase-matching challenge.
Hassan and his colleagues developed a four-wave mixing-based approach to create these extremely short light bursts. Multiple lights interact and merge in this method. Building on Hassan's ultrafast pulse work, the team created superfast compressed light by splitting a laser into three identical beams and focusing them on fused silica.
Squeeze Control in Real Time
Previous strategies focused on limiting photon phase and wavelength uncertainty to produce ultrafast squeezed light. In a novel move, Hassan's group compressed photon intensity.
Most notably, they revealed how to switch between intensity- and phase-squeezing by orienting the fused silica relative to the split laser beam. When silica is perpendicular, photons arrive simultaneously. A slight incidence angle shift delays one photon. This minor angle adjustment controls the squeeze.
This flexibility is crucial, Hassan said, “This is the first real-time measurement and control of quantum uncertainty, and the first demonstration of ultrafast squeezed light.”
Increasing Communication Speed and Security
The group has employed their safe communication approach. Ultrafast and compressed light pulses have been used separately to carry binary data, but combining them increases speed and security.
Quantum light provides security. If someone intercepts quantum light data, the network can detect it quickly. With prior methods, a hacker may learn some information with a decoding key.
The UA team's unique method requires the eavesdropper to interrupt the quantum state and know the pulse amplitude and key. Since the intruder interferes with amplitude squeezing, decoded data is incorrect since they cannot estimate the uncertainty.
In addition to secure communications, Hassan believes ultrafast quantum light will advance chemistry, biology, and quantum sensing. More accurate diagnostics, ultrasensitive environmental monitoring detectors, and new drug development may be possible.
