The query of where the boundary between classical and quantum physics lies is one among the longest-standing pursuits of recent scientific research and in latest research published today, scientists show a novel platform that might help us find a solution.
The laws of quantum physics govern the behaviour of particles at miniscule scales, resulting in phenomena resembling quantum entanglement, where the properties of entangled particles turn into inextricably linked in ways that can’t be explained by classical physics.
Research in quantum physics helps us to fill gaps in our knowledge of physics and may give us a more complete picture of reality, however the tiny scales at which quantum systems operate could make them difficult to look at and study.
Over the past century, physicists have successfully observed quantum phenomena in increasingly larger objects, all the way in which from subatomic particles like electrons to molecules which contain 1000’s of atoms.
More recently, the sphere of levitated optomechanics, which deals with the control of high-mass micron-scale objects in vacuum, goals to push the envelope further by testing the validity of quantum phenomena in objects which can be several orders of magnitude heavier than atoms and molecules. Nevertheless, because the mass and size of an object increase, the interactions which lead to delicate quantum features, resembling entanglement, wander off to the environment, leading to the classical behaviour we observe.
But now, the team 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 brand new approach to beat this problem in an experiment carried out at ETH Zurich, published within the journal Nature Physics.
Dr Vijayan said: “To look at quantum phenomena at larger scales and make clear the classical-quantum transition, quantum features should be preserved within the presence of noise from the environment. As you possibly can imagine, there are two ways to do this- one is to suppress the noise, and the second is to spice up the quantum features.
“Our research demonstrates a method 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 could be amplified by several orders of magnitude to beat losses to the environment.”
The scientists placed the particles between two highly reflective mirrors which form an optical cavity. This fashion, the photons scattered by each particle bounce between the mirrors several thousand times before leaving the cavity, resulting in a significantly higher likelihood of interacting with the opposite particle.
Johannes Piotrowski, co-lead of the paper from ETH Zurich added: “Remarkably, since the optical interactions are mediated by the cavity, its strength doesn’t decay with distance meaning we could couple micron-scale particles over several millimetres.”
The researchers also show the remarkable ability to finely adjust or control the interaction strength by various the laser frequencies and position of the particles inside the cavity.
The findings represent a big leap towards understanding fundamental physics, but additionally hold promise for practical applications, particularly in sensor technology that might be used towards environmental monitoring and offline navigation.
Dr Carlos Gonzalez-Ballestero, a collaborator from the Technical University of Vienna said: “The important thing 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, leading to higher sensitivity. As such, quantum sensors could be utilized in many alternative applications in various fields, resembling monitoring polar ice for climate research and measuring accelerations for navigation purposes.”
Piotrowski added: “It’s exciting to work on this relatively latest platform and test how far we will push it into the quantum regime.”
Now, the team of researchers will mix the brand new capabilities with well-established quantum cooling techniques in a stride towards validating quantum entanglement. If successful, achieving entanglement of levitated nano- and micro-particles could narrow the gap between the quantum world and on a regular basis classical mechanics.
On the Photon Science Institute and the Department of Electrical and Electronic Engineering at The University of Manchester, Dr Jayadev Vijayan’s team will proceed working in levitated optomechanics, harnessing interactions between multiple nanoparticles for applications in quantum sensing.
