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We present a generic system of three harmonic modes coupled parametrically with a time-varying coupling modulated by a combination of two pump harmonics, and show how this system provides the minimal platform to realize nonreciprocal couplings that can lead to gainless photon circulation, and phase-preserving or phase-sensitive directional amplification. Explicit frequency-dependent calculations within this minimal paradigm highlight the separation of amplification and directionality bandwidths, universal in such schemes. We also study the influence of counter-rotating interactions that can adversely affect directionality and associated bandwidth; we find that these effects can be mitigated by suitably designing the properties of the auxiliary mode that plays the role of an engineered reservoir to the amplification mode space.
We propose how to achieve synthetic $mathcal{PT}$ symmetry in optomechanics without using any active medium. We find that harnessing the Stokes process in such a system can lead to the emergence of exceptional point (EP), i.e., the coalescing of both
Spins in silicon quantum devices are promising candidates for large-scale quantum computing. Gate-based sensing of spin qubits offers compact and scalable readout with high fidelity, however further improvements in sensitivity are required to meet th
Directional transport is obtained in various multimode systems by driving multiple, nonreciprocally-interfering interactions between individual bosonic modes. However, systems sustaining the required number of modes become physically complex. In our
We derive quantum constraints on the minimal amount of noise added in linear amplification involving input or output signals whose component operators do not necessarily have c-number commutators, as is the case for fermion currents. This is a genera
Topological Weyl semimetals (TWS) can be classified as type-I TWS, in which the density of states vanishes at the Weyl nodes, and type-II TWS where an electron and a hole pocket meet with finite density of states at the nodal energy. The dispersions