Quantum optical phenomena give rise to various effects that can be harnessed technologically, such as leveraging cavity quantum electrodynamics for ultra-sensitive plasmonic biosensors. Plexcitons – a quantum optical phenomenon – result from the coherent coupling between plasmons and excitons, and may be applied in diverse applications such as photocatalysts, solar cells, and optoelectronic devices. The feasibility of any technological application of quantum optical phenomena hinges on having a controllable and reliable source of photons that operates at room temperature and is easily scaled down to the nanoscale.
To date, the various proposed photon sources based on cavity quantum electrodynamics rely on one of two generation mechanisms: (i) the conventional photon blockade mechanism yields a stream of single photons (i.e. antibunched), or (ii) the unconventional photon blockade mechanism that emits either one photon, or bunches of three or more photons simultaneously (i.e. antipaired, as the simultaneous emission of two photons is suppressed). While there had been many proposed photon sources based on cavity quantum electrodynamics, all the current proposals are operational only at low temperatures, with some only at cryogenic temperatures.
Building on recent experimental demonstrations of conventional photon blockade, and in separate experiments, measurements of unconventional photon blockade effects, this paper leverages analytical calculations to present a theoretical proof-of-concept of a photon source – consisting of a plasmonic cavity and two different emitters – that operates at room temperature, and is capable of freely switching between the conventional and unconventional photon blockade mechanisms, entirely controlled by the coupling between the plasmonic cavity and any one of the two emitters.
Two realistic schemes for realising such a switchable photon source – one chemical and one optical – are also described: the chemical approach directly changes the properties of the emitters, while the optical scheme externally varies the electric field distributions of the plasmonic cavity so as to change the coupling rate of the emitters at different locations. To the best of our knowledge, this is the first theoretical proposal for a single-photon source for operation at room temperature and scalable down to the nanoscale, as well as the first proposal for a single-photon source capable of switching between two fundamentally different emission mechanisms.
This work on photon sources, supported by two NRF and one SERC grant in quantum systems and nanoplasmonics, is part of IHPC's broader contribution to quantum science and technology ecosystem in Singapore – quantum key distribution and quantum random number generation rely on single photons for secure quantum communication, while quantum metrology and sensing exploit wave packets of a fixed number of photons to achieve enhanced sensitivity and energy efficiency. Future IHPC work could explore leveraging plexcitonics for quantum devices (e.g. quantum logic gates) designed specifically for room temperature operation, and biosensors.
The article titled "Reconfigurable Photon Sources Based on Quantum Plexcitonic Systems" was published in Nano Letters
(impact factor of 11.238) by researchers from IHPC, Sun Yat-sen University, Peking University, Wuhan Institute of Physics and Mathematics, Universidad Autonoma de Madrid, and NUS. The IHPC researchers involved in this work are Dr You Jiabin, Dr Xiong Xiao, Dr Bai Ping, Dr Jason Png and Dr Wu Lin.