Sensors are a constant feature of our everyday lives. Although they often go unperceived, sensors provide critical information essential to modern healthcare, security, and environmental monitoring. Modern cars alone contain over 100 sensors and this number will only increase. Quantum sensing is poised to revo­lutionize today's sensors, signi­ficantly boosting the performance they can achieve. More precise, faster, and reliable measurements of physical quantities can have a trans­formative effect on every area of science and technology, including our daily lives. 

However, the majority of quantum sensing schemes rely on special entangled or squeezed states of light or matter that are hard to generate and detect. This is a major obstacle to har­nessing the full power of quantum-limited sensors and deploying them in real-world scenarios. Now, a team of physicists at the Univer­sities of Bristol, Bath and Warwick have shown it is possible to perform high precision measurements of important physical properties without the need for sophis­ticated quantum states of light and detection schemes. 

The key to this breakthrough is the use of ring resonators – tiny racetrack structures that guide light in a loop and maximize its inter­action with the sample under study. Importantly, ring resonators can be mass manufactured using the same processes as the chips in our computers and smart­phones. Alex Belsley, Quantum Engi­neering Techno­logy Labs (QET Labs) PhD student, said: “We are one step closer to all integrated photonic sensors operating at the limits of detection imposed by quantum mechanics.” 

Employing this techno­logy to sense absorption or refractive index changes can be used to identify and characterize a wide range of materials and biochemical samples, with topical applications from moni­toring green­house gases to cancer detection. Jonathan Matthews, co-Director of QET Labs, stated: “We are really excited by the oppor­tunities this result enables: we now know how to use mass manu­facturable processes to engineer chip scale photonic sensors that operate at the quantum limit.” (Source: U. Bristol)

Reference: A. Belsley et al.: Advantage of Coherent States in Ring Resonators over Any Quantum Probe Single-Pass Absorption Estimation Strategy, Phys. Rev. Lett. 128, 230501 (2022); DOI: 10.1103/PhysRevLett.128.230501

Link: Quantum Engineering Technology Labs, University of Bristol, Bristol, United Kingdom