Program

LSU SQuInT Event Map

SESSION 8: Quantum optics theory (Theatre)

Chair: (Pablo Barberis Blostein (Univ. Nacional Autonoma de Mexico))
1:30pm - 2:15pmSaikat Guha, Raytheon BBN Technologies
Fundamental percolation thresholds for ballistic linear optical quantum computing

Abstract. Any quantum algorithm can be implemented by an adaptive sequence of single node measurements on an entangled cluster of qubits in a square lattice topology. Photons are a promising candidate for encoding qubits but assembling a photonic entangled cluster with linear optical elements relies on probabilistic operations.

2:15pm - 2:45pmLeonid Isaev, JILA, NIST, CU Boulder
Decoherence-free quantum computing in Kondo-coupled optical tweezers

Abstract. We propose a basis for decoherence-free quantum computing that uses neutral atoms and encodes qubits in the collective atomic spin and motional degrees of freedom. The physical qubit consists of three spin-\(\frac{1}{2}\) atoms in a double-well, two localized in the lowest vibrational mode and one atom in an excited delocalized state, subject to a staggered Zeeman field whose direction is opposite in the two traps. An interplay between this field gradient and exchange interactions gives rise to a local singlet-triplet degeneracy, and defines a logical qubit subspace. For strong interactions this subspace enjoys full protection against longitudinal magnetic-field noise, and is protected by an energy gap against transverse spin-flipping perturbations. Arbitrary single-qubit rotations are performed by virtue of resonant transfer of two-atom singlet-triplet states between the wells. Moreover, a two-qubit entangling control-z gate can be implemented. We design a qubit initialization protocol that employs Landau-Zener adiabatic tunneling to efficiently create a spin-singlet state in one well, and argue that our proposal can be realized using optical tweezers to create the double-well, hyperfine states of bosonic \(^{87} {\rm Rb}\) atoms to implement spin degrees of freedom, and laser-induced AC Stark shifts to impose the Zeeman field gradient.

2:45pm - 3:15pmXiaodong Qi, CQuIC, New Mexico
Spin squeezing on nanophotonic waveguides

Abstract. Strong coupling between atoms and photons is a prerequisite for quantum information processing protocols ranging from quantum metrology to quantum communication and computation. This strong coupling effect can be achieved using nanophotonic waveguides whereby an ensemble of atoms are trapped in the evanescent field. In this talk, I will present our recent progress in the theoretical study of implementing spin squeezing using optical nanofibers (ONF) and square waveguides (SWG) with both birefringence and Faraday interactions as QND measurement. Various geometries of protocols will be discussed based on the analysis of optical depth per atom on ONF and SWG platforms. In calculating the spin squeezing parameter, we have established a set of stochastic master equations to describe the individual and collective spin dynamics. Our simulation shows that ~10 dB of spin squeezing can be reached with a few thousands of atoms on these nanophotonic waveguides. Using the fundamental TE and TM modes, the SWG could generate more spin squeezing compared to the ONF platform. Our result can be generalized to other nanophotonic platforms, for the implementation of non-Gaussian states, and to improve quantum sensing precision using spin squeezing techniques.

SQuInT Chief Organizer
Akimasa Miyake, Assistant Professor
amiyake@unm.edu

SQuInT Co-Organizer
Mark M. Wilde, Assistant Professor LSU
mwilde@phys.lsu.edu

SQuInT Administrator
Gloria Cordova
gjcordo1@unm.edu
505 277-1850

SQuInT Event Coordinator
Karen Jones, LSU
kjones@cct.lsu.edu

SQuInT Founder
Ivan Deutsch, Regents' Professor
ideutsch@unm.edu

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