Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session TT06: V: Open Quantum Systems |
Hide Abstracts |
Sponsoring Units: DAMOP Chair: Linda Reichl, University of Texas at Austin Room: Virtual Room 6 |
Tuesday, March 21, 2023 3:30PM - 3:42PM |
TT06.00001: A Hermitian bypass to the non-Hermitian quantum theory Priyanshi Bhasin, Tanmoy Das With the emergence of phenomena explainable only through non-Hermiticity and their potential applications in quantum technologies, the demand for a systematic theory of such operators has become unavoidable. In this work, we study a class of non-Hermitian Hamiltonians (H) in which {H, H†} can be made a dynamical symmetry. By constructing a bilinear Hermitian operator, F= H†H, we build a computational basis bounded by exceptional points. Expressing the energy eigenstates in this computational basis, we discover that (a) the energy eigenstates meet at the exceptional points when they collapse to any one of the computational basis states, (b) the biorthogonal dual space can be mapped via a discrete “space-time” transformation and (c) the energy eigenstates display an intrinsic entanglement in the computational space. Extending these results to odd-dimension Hilbert spaces, the computational basis leads to an irreducible representation where one eigenstate exhibits parameter-free energy, whereas the others follow the same theory as for even-dimensions. |
Tuesday, March 21, 2023 3:42PM - 3:54PM |
TT06.00002: Linearly Driven Non-Hermitian Quantum Systems Julia Cen, Rajesh Malla, Wilton Kort-Kamp, Avadh B Saxena Many-body generalization of the Landau-Zener models, known as multi-state Landau-Zener models have been extensively investigated in Hermitian physics with applications in various physical systems. In this work, we extend investigations to the non-Hermitian regime, where the non-Hermiticity is introduced through anti-Hermitian couplings. We provide a framework on how to solve non-Hermitian multi-state Landau-Zener models with illustrative examples of 4-level and 6-level quantum systems. Moreover, we discuss the potential application of the non-Hermitian multi-state Landau-Zener model in coupled optical waveguides. |
Tuesday, March 21, 2023 3:54PM - 4:06PM |
TT06.00003: Transient and nonequilibrium steady state of a periodically driven dissipative qubit Weijian Chen, Maryam Abbasi, Serra Erdamar, Yogesh N Joglekar, Kater Murch Floquet engineering can significantly modify the energy spectra of quantum systems and create novel states of matter, such as discrete time crystals observed in periodically driven many-body-localized systems. The interplay of periodic drive and energy dissipation of quantum systems further enriches the quantum dynamics and leads to nonequilibrium steady states. In this work, we study the transient dynamics of a periodically driven dissipative qubit towards its nonequilibrium steady state, which is determined by a (generically non-Hermitian) Floquet Liouvillian. The stroboscopic evolution, given by the qubit states at times equal to integer multiples of the drive period, exhibits a transition from oscillatory decay to exponential decay, indicating the occurrence of an exceptional point degeneracy of the Floquet Liouvillian. We further observe chiral nonequilibrium steady states by varying the drive parameters. Our work provides a new approach to studying exceptional points in dissipative quantum systems and may benefit state preparation and stabilization through Floquet engineering. |
Tuesday, March 21, 2023 4:06PM - 4:18PM |
TT06.00004: Turing instability of activator-inhibitor units in open quantum systems Yuzuru Kato, Hiroya Nakao We show that Turing instability, a fundamental mechanism of nonequilibrium self-organization in classical systems, can also occur in a open quantum system. We propose a degenerate parametric oscillator with nonlinear damping in quantum optics as a quantum activator–inhibitor unit and numerically demonstrate that a system of two such units can undergo Turing instability when diffusively coupled with each other. We also show that the Turing instability induces nonuniformity and entanglement between the two units and gives rise to a pair of nonuniform states that are mixed due to quantum noise. We further show that performing continuous measurement on the coupled system reveals the true asymmetry caused by the Turing instability. Our results extend the universality of the Turing mechanism to the quantum realm and may provide a novel perspective on the possibility of quantum nonequilibrium self-organization. |
Tuesday, March 21, 2023 4:18PM - 4:30PM |
TT06.00005: High accuracy steady states obtained from the Universal Lindblad Equation Frederik S Nathan We show that the universal Lindblad equation (ULE) captures steady-state expectation values of observables up to rigorously bounded corrections that scale linearly with the system-bath coupling, Γ. We moreover identify a simple quasilocal transformation, whose application guarantees a relative deviation generically scaling to zero with Γ, even for observables such as currents whose steady-state values themselves vanish in the weak coupling limit. This result provides a solution to recently identified limitations on the accuracy of Lindblad-form master equations, which imply significant relative errors for observables whose steady-state values vanish with Γ, while most generic observables are otherwise captured faithfully. The transformation allows for high-fidelity computation of sensitive observables while retaining the stability and physicality of a Lindblad-form master equation |
Tuesday, March 21, 2023 4:30PM - 4:42PM |
TT06.00006: Simulation of non-Hermitian dynamics of many-body quantum systems Anant V Varma We investigate the complexity of simulating many-body non-Hermitian dynamics using the embedding method, as non-Hermitian systems do not exist in nature as closed systems. We show that simulation of even simplest many-body non-Hermitian system namely a system of N-free spin-1/2s or fermions would require a strongly correlated Hermitian system in higher dimensions, with a minimal dilation of Hilbert space. We further show that such highly interacting Hermitian system can be visualized as a central spin or fermion model and exhibit many-body features like orthogonality catastrophe. |
Tuesday, March 21, 2023 4:42PM - 4:54PM |
TT06.00007: Nonlinearity and temperature dependence of drive-induced shifts in a thermal environment Arpan Chatterjee, Rangeet Bhattacharyya Drive-induced shifts, such as ac Stark shift and Bloch-Siegert shift, are routinely used in various |
Tuesday, March 21, 2023 4:54PM - 5:06PM |
TT06.00008: Non-Hermitian Absorption Spectroscopy Kai Li, Yong Xu While non-Hermitian Hamiltonians have been experimentally realized in cold atom systems, it remains an outstanding open question of how to experimentally measure their complex energy spectra in momentum space for a realistic system with boundaries. The existence of non-Hermitian skin effects may make the question even more difficult to address given the fact that energy spectra for a system with open boundaries are dramatically different from those in momentum space; the fact may even lead to the notion that momentum-space band structures are not experimentally accessible for a system with open boundaries. Here, we generalize the widely used radio-frequency spectroscopy to measure both real and imaginary parts of complex energy spectra of a non-Hermitian quantum system for either bosonic or fermionic atoms. By weakly coupling the energy levels of a non-Hermitian system to auxiliary energy levels, we theoretically derive a formula showing that the decay of atoms on the auxiliary energy levels reflects the real and imaginary parts of energy spectra in momentum space. We further prove that measurement outcomes are independent of boundary conditions in the thermodynamic limit, providing strong evidence that the energy spectrum in momentum space is experimentally measurable. We finally apply our non-Hermitian absorption spectroscopy protocol to the Hatano-Nelson model and non-Hermitian Weyl semimetals to demonstrate its feasibility. |
Tuesday, March 21, 2023 5:06PM - 5:18PM |
TT06.00009: Frustrated Superradiant Phase Transition Jinchen Zhao, Myung-Joong Hwang Frustration occurs when a system cannot satisfy competing interactions. In this talk, we introduce a frustrated superradiant phase transition [1] that occurs when the ground-state coherence of bosonic modes due to the strong local qubit-boson interaction cannot simultaneously minimize the positive hopping energies. As a model system, we consider the Dicke trimer model with negative and positive hopping energy and show that the latter leads to a sixfold degenerate ground-state manifold where the translational symmetry is spontaneously broken by frustration. Moreover, we find two sets of diverging time and fluctuation scales coexist in the frustrated superradiant phase. In addition to the mean-field critical mode present in the non-frustrated superradiant phase, a frustrated mode with a novel critical exponent emerges. The new critical exponent is associated with the fluctuation in the difference between local order parameters, which results in site-dependent photon number critical exponents. We provide the physical intuition behind the exotic critical scaling and generalize it to a Dicke lattice system with an odd number of sites. Our study paves the way to study frustrated phases of light-matter systems, as the frustration mechanism identified here can be applied to any lattice system where the antiferromagnetic ordering is incompatible with the lattice geometry. |
Tuesday, March 21, 2023 5:18PM - 5:30PM |
TT06.00010: Polarization-correlated narrowband photon pair generation in a fiber-pigtailed MgO:ppLN ridge waveguide Akanksha Angural, Ramesh Kumar, Joyee Ghosh Spontaneous parametric down-conversion (SPDC) based waveguide sources are widely used to generate heralded single photons or paired photons of lower frequency for various applications in quantum technology. In this work, we present a narrowband spectral and polarization-correlated photon-pair source around telecom wavelength 1560 nm based on type II quasi phase-matched, fiber-pigtailed, MgO-doped periodically poled lithium niobate (MgO:ppLN) ridge waveguide module of length ~1.69 cm. Waveguide-based SPDC sources have gained popularity as they offer better confinement of spatial modes, thus enhancing the degree of nonlinear interactions leading to an increase in the brightness of generated photons. Fiber-pigtailing such sources offer compact solutions and can increase the commercial viability of quantum systems. A type II phase-matched waveguide generates narrowband orthogonal photon pairs thus, fiber coupling such sources can be complicated compared to other types. Hence, photon pair generation using type II fiber-pigtailed waveguides has not been explored sufficiently to the best of our knowledge. We have demonstrated an efficient photon-pair source with the following characteristics: a measured phase-matched bandwidth of 0.6nm, a spectral brightness of ~7.79×104 pairs/sec/mW/nm and a coincidence-to-accidental ratio (CAR) of ~246. This source can be potentially used in commercial long-distance quantum communication systems owing to its compact, narrowband and reliable nature. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700