Speaker :  RayKuang Lee (National TsingHua University) 
Title :  Reflecting on an alternative (paritytimesymmetric) quantum theory, and its analog in optics 
Time :  20180320 (Tue) 11:0012:30 
Place :  Seminar Room 617, Institute of Mathematics (NTU Campus) 
Abstract: 
By nosignaling principle, we showed that paritytime (PT)symmetric quantum theory as an extension of the quantum theory to nonHermitian Hamiltonians is either a trivial extension or likely false as a fundamental theory [1]. In addition to the implementation PTsymmetric optical systems by carefully and actively controlling the gain and loss, we show that a 2 × 2 PTsymmetric Hamiltonian has a unitarily equivalent representation without complex optical potentials in the resulting optical coupler. Through the Naimark dilation in operator algebra, passive PTsymmetric couplers can thus be implemented with a refractive index of real values and asymmetric coupling coefficients [2]. Moreover, with a phasespace representation on the vicinity of an exceptional point, we show that a PTsymmetric phase transition from an unbroken PTsymmetry phase to a broken one is a secondorder phase transition [3].
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