Title: Understanding Quantum Decoherence with Ultracold Molecule Quantum Simulator Interaction Networks: From Field Control to Reservoir Engineering

Speaker: Lincoln Carr

Abstract: Ultracold molecules are a key quantum simulator architecture [1].  They are trapped in optical lattices or optical tweezers and naturally give rise to multi-layer complex networks via long-range dipole-dipole interactions.  These interaction networks are highly state-dependent and can be controlled via external electric and magnetic fields [2].  Molecules have been measured to have extremely long coherence times of milliseconds to seconds.  Because ultracold molecules also exist in tightly controlled environments, reservoir engineering can be used to actively study decoherence.  This talk will present the building blocks of a proposed study on the interface between controlled quantum elements in the form of ultracold molecules [2], their interaction networks [3], and their internal decoherence (or dephasing) and external decoherence with engineered reservoirs [4].  A key preliminary result is the number of qubits one can classically simulate for open quantum systems is reduced by a factor of 4 due to entanglement incurred by the interaction network, in turn showing quantum advantage for 12-13 qubits, or even a few qudits, for open quantum systems as opposed to closed ones.  Moreover, small finite scaling studies indicate a subradiant effect in which, counter-intuitively, more molecules actually limits decoherence [4].  Thus, our results encourage open quantum system exploration in noisy intermediate-scale quantum technologies, with ultracold molecules presenting an ideal physical architecture.

References:

1. Ehud Altman, et al., “Quantum Simulators: Architectures and Opportunities,” Physical Review X Quantum, v. 2, p. 017003 (2020), https://doi.org/10.1103/PRXQuantum.2.017002  
2. L. D. Carr, David DeMille, Roman V. Krems, and Jun Ye, “Cold and Ultracold Molecules: Science, Technology, and Applications,” New J. Phys. v. 11, p. 055049 (2009), http://dx.doi.org/10.1088/1367-2630/11/5/055049
3. Bhuvanesh Sundar, Mattia Walschaers, Valentina Parigi, and Lincoln D Carr, “Response of quantum spin networks to attacks,” J. Phys. Complexity, in press (2021), https://doi.org/10.1088/2632-072X/abf5c2
4. Daniel Jaschke, Lincoln D. Carr, and Ines de Vega, “Thermalization in the quantum Ising model—approximations, limits, and beyond,” Quantum Science and Technology 4, 034002 (2019), https://doi.org/10.1088/2058-9565/ab1a71