Where the boundary between classical and quantum physics lies is one of science’s greatest mysteries, and in new research, scientists have unveiled a new platform that could find the answer.
A team of researchers, co-led by Dr Jayadev Vijayan, Head of the Quantum Engineering Lab at The University of Manchester, with scientists from ETH Zurich and theorists from the University of Innsbruck, have established a new approach that can shed light on the transition from classical to quantum physics.
The platform will also help physicists observe quantum phenomena at larger scales.
The work is published in the journal Nature Physics.
What can quantum physics tell us?
The laws of quantum physics govern the behaviour of particles at minuscule scales. This leads to phenomena such as quantum entanglement, where the properties of entangled particles become linked in ways that cannot be explained by classical physics.
Research in quantum physics can help us to fill gaps in our knowledge of physics and give us a more complete picture of reality.
However, the tiny scales at which quantum systems operate can make them difficult to observe and study.
Observing quantum phenomena in larger objects
Over the past century, physicists have observed quantum phenomena in increasingly larger objects. For example, from subatomic particles like electrons to molecules that contain thousands of atoms.
More recently, the field of levitated optomechanics aims to push the envelope further by testing the validity of quantum phenomena in objects that are several orders of magnitude heavier than atoms and molecules.
However, as the mass and size of an object increase, the interactions result in delicate quantum features getting lost to the environment. This results in the classical behaviour we observe.
Dr Vijayan said: “To observe quantum phenomena at larger scales and shed light on the classical-quantum transition, quantum features need to be preserved in the presence of noise from the environment.
“As you can imagine, there are two ways to do this- one is to suppress the noise, and the second is to boost the quantum features.
“Our research demonstrates a way to tackle the challenge by taking the second approach. We show that the interactions needed for entanglement between two optically trapped 0.1-micron-sized glass particles can be amplified by several orders of magnitude to overcome losses to the environment.”
The team’s work
The scientists placed the particles between two highly reflective mirrors, which form an optical cavity. This way, the photons scattered by each particle bounce between the mirrors several thousand times before leaving the cavity.
This leads to a significantly higher chance of interacting with the other particle.
Johannes Piotrowski, co-lead of the paper from ETH Zurich, added: “Remarkably, because the optical interactions are mediated by the cavity, its strength does not decay with distance, meaning we could couple micron-scale particles over several millimetres.”
The team can also adjust or control the interaction strength by varying the laser frequencies and position of the particles within the cavity.
A leap towards understanding fundamental physics
The findings represent a significant leap towards understanding fundamental physics. They also hold promise for practical applications, particularly in sensor technology.
This technology can be used towards environmental monitoring and offline navigation.
Dr Carlos Gonzalez-Ballestero, a collaborator from the Technical University of Vienna, said: “The key strength of levitated mechanical sensors is their high mass relative to other quantum systems using sensing. The high mass makes them well-suited for detecting gravitational forces and accelerations, resulting in better sensitivity.
“As such, quantum sensors can be used in many different applications in various fields, such as monitoring polar ice for climate research and measuring accelerations for navigation purposes.”
Next steps for the researchers
Now, the team of researchers will combine the new capabilities with well-established quantum cooling techniques. If successful, achieving entanglement of levitated nano- and micro-particles could bridge the barrier between quantum and classical physics.
The University of Manchester’s team will continue working in levitated optomechanics, harnessing interactions between multiple nanoparticles for applications in quantum sensing.
