TY - JOUR T1 - Photon pair condensation by engineered dissipation JF - Phys. Rev. Lett. Y1 - 2019 A1 - Ze-Pei Cian A1 - Guanyu Zhu A1 - Su-Kuan Chu A1 - Alireza Seif A1 - Wade DeGottardi A1 - Liang Jiang A1 - Mohammad Hafezi AB -

Dissipation can usually induce detrimental decoherence in a quantum system. However, engineered dissipation can be used to prepare and stabilize coherent quantum many-body states. Here, we show that by engineering dissipators containing photon pair operators, one can stabilize an exotic dark state, which is a condensate of photon pairs with a phase-nematic order. In this system, the usual superfluid order parameter, i.e. single-photon correlation, is absent, while the photon pair correlation exhibits long-range order. Although the dark state is not unique due to multiple parity sectors, we devise an additional type of dissipators to stabilize the dark state in a particular parity sector via a diffusive annihilation process which obeys Glauber dynamics in an Ising model. Furthermore, we propose an implementation of these photon-pair dissipators in circuit-QED architecture. 

VL - 123 UR - https://arxiv.org/abs/1904.00016 CP - 063602 U5 - 10.1103/PhysRevLett.123.063602 ER - TY - JOUR T1 - Thermal management and non-reciprocal control of phonon flow via optomechanics JF - Nat. Commun. Y1 - 2018 A1 - Alireza Seif A1 - Wade DeGottardi A1 - Keivan Esfarjani A1 - Mohammad Hafezi AB -

Engineering phonon transport in physical systems is a subject of interest in the study of materials and plays a crucial role in controlling energy and heat transfer. Of particular interest are non-reciprocal phononic systems, which in direct analogy to electric diodes, provide a directional flow of energy. Here, we propose an engineered nanostructured material, in which tunable non-reciprocal phonon transport is achieved through optomechanical coupling. Our scheme relies on breaking time-reversal symmetry by a spatially varying laser drive, which manipulates low-energy acoustic phonons. Furthermore, we take advantage of recent developments in the manipulation of high-energy phonons through controlled scattering mechanisms, such as using alloys and introducing disorder. These combined approaches allow us to design an acoustic isolator and a thermal diode. Our proposed device will have potential impact in phonon-based information processing, and heat management in low temperatures. 

VL - 9(1) UR - https://arxiv.org/abs/1710.08967 CP - 1207 U5 - https://doi.org/10.1038/s41467-018-03624-y ER -