Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Z33: Open Quantum Systems IIIFocus Recordings Available
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Sponsoring Units: DAMOP Chair: Ricardo Gutierrez-Jauregui, Columbia University Room: McCormick Place W-192C |
Friday, March 18, 2022 11:30AM - 11:42AM |
Z33.00001: Unidirectional transport of light along an atomic waveguide Ricardo Gutierrez-Jauregui, Ana Asenjo-Garcia Optical isolators that permit transport of light in one direction and block it in the opposite are a subject of considerable interest. Motivated by a recent prediction to engineer the dispersion relation of a waveguide constructed from atomic components, the possibility to create directional transport in an open, collective quantum system can now be explored. In this talk I will review an idealized model for an atomic chain whose optical response is engineered to display directionality. I will discuss a scattering formulation where mode-to-mode transmissions are readily calculated to fully characterize the optical response. Once the conditions for directionality are established, I explore how to retrieve excitations efficiently from a directional chain. To finish, I will include the effect of imperfections that break the periodicity of the array and show that backscattering is suppressed even in the presence of strong noise for a directional chain. |
Friday, March 18, 2022 11:42AM - 11:54AM |
Z33.00002: Double-driven Parity-Time (PT) and Anti-Parity-Time (APT) Symmetric Floquet Models Julia Cen, Yogesh N Joglekar, Avadh B Saxena In quantum mechanics, one of the key requirements for a system is that it must be Hermitian in order to have real energies and unitary time evolution. Over the past two decades, we have seen tremendous growth of interest in systems that are non-Hermitian, but PT-symmetric. This is due to the fact they have been found to possess real energies, although being open systems, hence generalizing the Hermiticity condition. More recently, there has been increasing interest in non-Hermitian systems with APT-symmetry, which has also been found in many contexts such as optics, diffusive systems, and electronics. In this talk, we will explore various types of single and double-driven time-periodic non-Hermitian PT and APT-symmetric Hamiltonians. Time-dependent systems are generally difficult to solve, but being time-periodic, we can resort to using Floquet theory for our models. PT and APT symmetries in the models give rise to transitions of PT-symmetry breaking and restoring, which as a result leads to observations of many fascinating and rich features and characteristics not seen in Hermitian cases. This could bring about new exciting developments to the probing and control of quantum systems. |
Friday, March 18, 2022 11:54AM - 12:06PM |
Z33.00003: Protocols for cooling with reservoirs strongly coupled to a system Azadeh Mazloom, James K Freericks In conventional theories of reservoirs coupled to systems, the reservoir is infinitely large and couples with an infinitesimally small coupling to the system. This allows it to exchange energy without modifying the properties of the system, ultimately leading to thermal equilibrium. In quantum computing, we would like to design cooling qubits that rapidly cool a system. But, because we only have a small number of qubits available, we must couple the reservoir strongly to the system. An ion-trap simulator is ideal for examining this behavior. We consider the ions at the end as the reservoir and the ions in the center as the system. It is a transverse-field Ising model with long-range interactions, which creates a strongly coupled reservoir-system. Our protocol is to start the bath sites in a low-energy state, wait, and then reset them back to a low-energy state at specific times. We show that this procedure makes the middle system reach close to its ground state. The efficiency of such cooling strongly depends on the reset rate and the strength of the system-bath coupling. By looking into the average of the spin, both along the Ising coupling direction and along the field direction, we can optimally predict the reset times in order to evolve the system closer to the ground state. |
Friday, March 18, 2022 12:06PM - 12:18PM |
Z33.00004: Locality of physical noise in quantum rigid rotors Shubham Jain, Victor V Albert Molecular rotational state spaces, modeled by infinite dimensional Hilbert spaces of quantum rigid rotors, present new grounds for encoding qubits with reliable error correction. They are, however, prone to noise induced by the environment via rotational friction and diffusion. As a step towards making qubits realizable through these rotor space configurations, we study the nature of noise introduced by a thermal environment in these systems. For the simpler setting of a planar rotor, we confirm that physical errors are local in the rotor's angular position and momentum phase space. Our analysis can be extended to the more general case of the completely asymmetric rigid rotor whose basis states are described by elements of the non-abelian group SO(3). |
Friday, March 18, 2022 12:18PM - 12:30PM |
Z33.00005: Exact description of quantum stochastic models as quantum resistors João S Ferreira, Tony Jin, Michele Filippone, Thierry Giamarchi Diffusion is one of the most common transport phenomena at hydrodynamic scales, both in classical and quantum systems. Yet, how exactly diffusion emerges from the underlying microscopic theory in a quantum system is still an exciting open question. In this talk, we present a new method to derive the transport properties of diffusive/ohmic quantum systems connected to fermionic reservoirs. The method is based on the expansion of the current in terms of the inverse system size using Keldysh formalism. We apply it to a large class of exactly solvable quantum stochastic Hamiltonians (QSHs) with time and space-dependent noise. These models confirm the validity of our system size expansion ansatz and its efficiency in capturing the transport properties. In particular, we consider three fermionic models: i) a model with local dephasing ii) the quantum simple symmetric exclusion process model iii) a model with long-range stochastic hopping. As a by-product, our approach equally describes the mean behavior of quantum systems under continuous measurement. |
Friday, March 18, 2022 12:30PM - 1:06PM |
Z33.00006: Measuring the Earth's rotation using a chip-scale Brillouin laser gyroscope Invited Speaker: Kerry J Vahala Counter-propagating lightwaves within a closed rotating loop enable rotation measurement as a result of the Sagnac effect. And modern optical gyroscopes use long coiled optical fiber paths (fiber optic gyroscopes) or resonant recirculation (ring laser gyroscopes) to greatly enhance this effect. In recent years, the possibility of chip-based optical gyroscopes has garnered considerable attention. Such integrated optical gyrocopes could enjoy the advantages of integration and scalable manufacturing, and would offer rugged designs for operation in challenging environments. Compact or chip-based ring laser gyroscopes, passive resonant gyroscopes, and interferometric gyroscopes have been reported. Here we first review some of the enabling technologies of chip-integrated designs, overview recent results, and then focus on a chip-based laser gyroscope that has been used to measure the Earth's rotation. The sensitivity of the gyroscope is limited by fundamental noise sources that are discussed. Also, operation of the gyroscope near an exceptional point is possible and the features of this mode of operation are reviewed. |
Friday, March 18, 2022 1:06PM - 1:18PM |
Z33.00007: Giant atoms in one-dimensional structured environments Ariadna Soro Álvarez, Carlos Sánchez Μuñoz, Anton Frisk Kockum Giant atoms (GAs) constitute a new paradigm in quantum optics in which they break the dipole approximation by coupling to light at multiple discrete points. They have been increasingly attracting attention for their ability to interact via a waveguide without decohering, which is why most previous work has been limited to GAs coupled to a one-dimensional (1D) continuous waveguide. Here, we instead consider GAs coupled to a 1D structured bath, e.g., an array of coupled cavities or a photonic crystal waveguide. This environment gives rise to a band structure, where atomic decay and interaction are highly dependent on the energy band to which the atoms are tuned. In particular, we study non-Markovian decay, time delay effects, formation of bound states and decoherence-free interaction, and we analyze how these phenomena are influenced by the number and distance of the GAs' coupling points to the bath. |
Friday, March 18, 2022 1:18PM - 1:30PM |
Z33.00008: Criticality and phase classification for quadratic open quantum many-body systems Yikang Zhang, Thomas Barthel We study the steady states of translation-invariant open many-body systems governed by Lindblad master equations, where the Hamiltonian is quadratic in the ladder operators, and the Lindblad operators are either linear or quadratic and Hermitian. We find that one-dimensional systems with short-range interactions cannot be critical, i.e., steady-state correlations necessarily decay exponentially. For the quasi-free case without quadratic Lindblad operators, we show that fermionic systems with short-range interactions are non-critical for any number of spatial dimensions and provide upper bounds on the correlation lengths. Lastly, we address the question of phase transitions in quadratic fermionic systems and find that, without symmetry constraints beyond particle-hole symmetries, all gapped Liouvillians belong to the same phase. |
Friday, March 18, 2022 1:30PM - 1:42PM |
Z33.00009: Non-reciprocal quantum interactions without real or synthetic magnetic fields Yuxin Wang, Aashish Clerk Non-reciprocal elements are a valuable resource in realizing scalable quantum circuits and networks. Conventional routes to non-reciprocity make crucial use of external magnetic fields or synthetic gauge fields (engineered, e.g., by dynamic modulation [1,2]). In the quantum case, the corresponding non-reciprocal interactions are ultimately described by a cascaded quantum-systems master equation [3,4]. Here, we discuss an alternate route to quantum non-reciprocity that does not necessarily require external magnetic fields (real or synthetic), and whose quantum dynamics is not described by a standard cascaded master equation. We show how an example of this dynamics can be realized in a regular circuit QED setup involving two cavities and a dispersively coupled qubit. We also show how this dynamics enables a number of new applications in quantum information processing, including a novel class of dissipative single- and two-qubit gates. Our ideas could be readily implemented in state-of-the-art superconducting qubit setups. |
Friday, March 18, 2022 1:42PM - 1:54PM |
Z33.00010: Non-equilibrium scalar field dynamics starting from Fock states: Absence of thermalization in one dimensional phonons coupled to fermions Md Mursalin Islam, Rajdeep Sensarma We propose a new method to study non-equilibrium dynamics of scalar fields starting from non-Gaussian initial conditions using Keldysh field theory. We use it to study dynamics of phonons coupled to non-interacting bosonic and fermionic baths, starting from initial Fock states. We find that in one dimension long wavelength phonons coupled to fermionic baths do not thermalize both at low and high bath temperatures. At low temperature, constraints from energy-momentum conservation lead to a narrow bandwidth of particle-hole excitations and the phonons effectively do not see this bath. On the other hand, the strong band edge divergence of particle-hole density of states leads to an undamped ``polariton-like'' mode of the dressed phonons above the band edge of the particle-hole excitations. These undamped modes contribute to the lack of thermalization of long wavelength phonons at high temperatures. In higher dimensions, these constraints and the divergence of density of states are weakened and leads to thermalization at all wavelengths. |
Friday, March 18, 2022 1:54PM - 2:06PM |
Z33.00011: Universal properties of dissipative Tomonaga-Luttinger liquids Kazuki Yamamoto, Masaya Nakagawa, Masaki Tezuka, Masahito Ueda, Norio Kawakami In recent years, open quantum systems have been actively studied both experimentally and theoretically, as exemplified by driven-dissipative systems and non-Hermitian (NH) quantum systems. In this talk, we demonstrate the universal properties of dissipative Tomonaga-Luttinger (TL) liquids by deriving correlation functions and performing finite-size scaling analysis for a NH XXZ spin chain as a prototypical correlated model in one-dimensional open quantum systems [1]. Our calculation is based analytically on the field theory, the finite-size scaling approach in conformal field theory, and the Bethe-ansatz solution, and numerically on the density-matrix renormalization group analysis generalized to NH systems (NH-DMRG). Importantly, we uncover that the model belongs to the universality class characterized by the complex-valued TL parameter in the massless regime with weak dissipation. On the other hand, the discrepancy in the TL parameter obtained by NH-DMRG and the Bethe-ansatz analysis indicates that the model becomes massive for strong dissipation. Our results can be tested in ultracold atoms by introducing two-body loss to the Bose-Hubbard model with photoassociation techniques [2]. |
Friday, March 18, 2022 2:06PM - 2:18PM |
Z33.00012: Time-delayed quantum feedback using a lattice of dissipative oscillators Xin Zhang, Sabine H. L. Klapp, Anja Metelmann Time-delayed quantum feedback has been a commonly used controlling method in quantum systems. However, solutions to these systems have been difficult to obtain due to their non-Markovian nature. Here, we show that time-delayed quantum feedback can be introduced with a novel setup, which is composed of a lattice of dissipative oscillators. This approach provides a novel viewpoint of time-delayed quantum dynamics and gives us accessibility to unexplored regimes. Further, with more tunability, it could find applications in quantum information processing. |
Friday, March 18, 2022 2:18PM - 2:30PM |
Z33.00013: Q-MARINA: Quantum Mapping Algorithm for a Resonator Interacting with N Atoms Marina Radulaski, Marina Krstic Marinkovic Tavis-Cummings (TC) cavity quantum electrodynamical effects in the low excitation regime are at the core of atomic, optical and solid state physics. The classical modeling of the open quantum TC systems is often limited to low-dimensional Hilbert spaces. Mapping this dynamic to a quantum circuit can expand the size of the system proportionally to the number of available qubits. We develop a gate-based quantum algorithm that simulates a system of two atoms in a resonant cavity. Subsequently, we devise a recipe for a quantum circuit that can model open quantum TC system of an arbitrary size. |
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