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Chemical potential for light



Jacob M. Taylor, Mohammad Hafezi, Prabin Adhikari


Photons are not conserved in interactions with other matter. Consequently, when understanding the equation of state and thermodynamics of photons, while we have a concept of temperature for energy conservation, there is no equivalent chemical potential for particle number conservation. However, the notion of a chemical potential is crucial in understanding a wide variety of single- and many-body effects, from transport in conductors and semi-conductors to phase transitions in electronic and atomic systems. Here we show how a direct modification of the system-bath coupling via parametric oscillation creates an effective chemical potential for photons even in the thermodynamic limit. Specific implementations, using circuit-QED or optomechanics, are feasible using current technologies, and we show a detailed example demonstrating the emergence of Mott Insulator-superfluid transition in a lattice of nonlinear oscillators. Our approach paves the way for quantum simulation, quantum sources and even electron-like circuits with light.
Nature Physics


parametric amplifier, quantum phase transition, quantum optics


Taylor, J. , Hafezi, M. and Adhikari, P. (2015), Chemical potential for light, Nature Physics, [online], (Accessed June 19, 2024)


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Created November 19, 2015, Updated June 2, 2021