Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSynthetic $mathcal{PT}$ Symmetry and Nonreciprocal Amplification in Optomechanics
99
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
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 the eigenvalues and the eigenvectors of the system. By encircling the EP,non-reciprocal optical amplification and chiral mode switching can be achieved. This provides a surprisingly simplified route to realize $mathcal{PT}$-symmetric optomechanics, indicating that a wide range of EP devices can be created and utilized for various applications such as topological optical engineering and nanomechanical processing or sensing.
rate research
Read More
Non-Hermitian systems, with symmetric or antisymmetric Hamiltonians under the parity-time ($mathcal{PT}$) operations, can have entirely real eigenvalues. This fact has led to surprising discoveries such as loss-induced lasing and topological energy transfer. A merit of anti-$mathcal{PT}$ systems is free of gain, but in recent efforts on making anti-$mathcal{PT}$ devices, nonlinearity is still required. Here, counterintuitively, we show how to achieve anti-$mathcal{PT}$ symmetry and its spontaneous breaking in a linear device by spinning a lossy resonator. Compared with a Hermitian spinning device, significantly enhanced optical isolation and ultrasensitive nanoparticle sensing are achievable in the anti-$mathcal{PT}$-broken phase. In a broader view, our work provides a new tool to study anti-$mathcal{PT}$ physics, with such a wide range of applications as anti-$mathcal{PT}$ lasers, anti-$mathcal{PT}$ gyroscopes, and anti-$mathcal{PT}$ topological photonics or optomechanics.
PT-symmetric scattering systems with balanced gain and loss can undergo a symmetry-breaking transition in which the eigenvalues of the non-unitary scattering matrix change their phase shifts from real to complex values. We relate the PT-symmetry breaking points of such an unbounded scattering system to those of underlying bounded systems. In particular, we show how the PT-thresholds in the scattering matrix of the unbounded system translate into analogous transitions in the Robin boundary conditions of the corresponding bounded systems. Based on this relation, we argue and then confirm that the PT-transitions in the scattering matrix are, under very general conditions, entirely insensitive to a variable coupling strength between the bounded region and the unbounded asymptotic region, a result that can be tested experimentally and visualized using the concept of Smith charts.
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 microwave-optomechanical experiment, we show how to configure nonreciprocal transport between frequency components of a single superconducting cavity coupled to two drumhead oscillators. The frequency components are promoted to Floquet modes and generate the missing dimension to realize an isolator and a directional amplifier. A second cavity left free by this arrangement is used to cool the mechanical oscillators and bring the transduction noise close to the quantum limit. We furthermore uncover a new type of instability specific to nonreciprocal coupling. Our approach is generic and can greatly simplify quantum signal processing and the design of topological lattices from low-dimensional systems.
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.
Over the past decade, parity-time ($mathcal{PT}$)-symmetric Hamiltonians have been experimentally realized in classical, optical settings with balanced gain and loss, or in quantum systems with localized loss. In both realizations, the $mathcal{PT}$-symmetry breaking transition occurs at the exceptional point of the non-Hermitian Hamiltonian, where its eigenvalues and the corresponding eigenvectors both coincide. Here, we show that in lossy systems, the $mathcal{PT}$ transition is a phenomenon that broadly occurs without an attendant exceptional point, and is driven by the potential asymmetry between the neutral and the lossy regions. With experimentally realizable quantum models in mind, we investigate dimer and trimer waveguide configurations with one lossy waveguide. We validate the tight-binding model results by using the beam propagation method analysis. Our results pave a robust way toward studying the interplay between passive $mathcal{PT}$ transitions and quantum effects in dissipative photonic configurations.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
