Francisella tularensis is a gram-negative facultative intracellular bacterium and the causative agent of tularemia. Two subspecies (type A and B strains) of the pathogen exist, the former being much more virulent than the latter for humans and other higher mammals. In this study, we examined the effect of virulent strains of F. tularensis infection on the thymus and thymocytes and the potential mechanisms involved. Low-dose aerosol exposure of C57BL/6 mice with type A, but not type B, F. tularensis caused severe reduction in thymus weight and destruction of thymocytes, particularly CD4 + CD8 + thymocytes, by day 4 after infection. The depletion of thymocytes was accompanied by a significant increase in circulating cortisone levels and could be partially prevented by adrenalectomy. Moreover, thymus atrophy and thymocyte depletion following infection were abolished in mice deficient in tumor necrosis factor receptors 1 and 2, but not in FasL-deficient mice. The severe destruction of the thymus and selective depletion of immature thymocytes during type A F. tularensis infection may represent a key pathogenic mechanism in tularemia and could hinder the development of an effective primary immune response against this highly virulent pathogen.

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Ultracold two-component Fermi gases with a tunable population imbalance have provided an excellent opportunity for studying the exotic Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states, which have been of great interest in condensed matter physics. However, the FFLO states have not been observed experimentally in Fermi gases in three dimensions (3D), possibly due to their small phase space volume and extremely low temperature required for an equal-mass Fermi gas. Here we explore possible effects of mass imbalance, mainly in a 6Li–40K mixture, on the one-plane-wave FFLO phases for a 3D homogeneous case at the mean-field level. We present various phase diagrams related to the FFLO states at both zero and finite temperatures, throughout the BCS-BEC crossover, and show that a large mass ratio may enhance substantially FFLO type of pairing.

The exotic Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states have been actively searched for experimentally since the mean-field based FFLO theories were put forward half a century ago. Here we investigate the stability of FFLO states against unavoidable pairing fluctuations, and conclude that FFLO superfluids cannot exist due to their intrinsic instability in three and two dimensions. This explains their absence in experimental observations in both condensed matter systems and the most recent, more promising ultracold atomic Fermi gases with a population imbalance.

Most matter-wave interferometry (MWI) schemes for quantum sensing have so far been evaluated in ideal situations without noises. In this work, we provide assessments of generic multiqubit MWI schemes under Markovian dephasing noises. We find that for certain classes of the MWI schemes with scale factors that are nonlinearly dependent on the interrogation time, the optimal precision of maximally entangled probes decreases with increasing the particle number N , for both independent and collective dephasing situations. This result challenges the conventional wisdom found in dephasing Ramsey-type interferometers. We initiate the analyses by investigating the optimal precision of multiqubit Sagnac atom interferometry for rotation sensing. And we show that due to the competition between the unconventional interrogation-time quadratic phase accumulation and the exponential dephasing processes, the Greenberger-Horne-Zeilinger (GHZ) state, which is the optimal input state in noiseless scenarios, leads to vanishing quantum Fisher information in the large-N regime. Then our assessments are further extended to generic MWI schemes for quantum sensing with entangled states and under decoherence. Finally, a quantum error-correction logical GHZ state is tentatively analyzed, which could have the potential to recover the Heisenberg scaling and improve the sensitivity. arXiv:1808.04632v3 [quant-ph]

We investigate quantum sensing of rotation with a multi-atom Sagnac interferometer and present multi-partite entangled states to enhance the sensitivity of rotation frequency. For studying the sensitivity, we first present a Hermitian generator with respect to the rotation frequency. The generator, which contains the Sagnac phase, is a linear superposition of a z component of the collective spin and a quadrature operator of collective bosons depicting the trapping modes, which enables us to conveniently study the quantum Fisher information (QFI) for any initial states. With the generator, we derive the general QFI which can be of square dependence on the particle number, leading to Heisenberg limit. And we further find that the QFI may be of biquadratic dependence on the radius of the ring which confines atoms, indicating that larger QFI is achieved by enlarging the radius. In order to obtain the square and biquadratic dependence, we propose to use partially and globally entangled states as inputs to enhance the sensitivity of rotation.

Quantum information processing with geometric features of quantum states may provide promising noiseresilient schemes for quantum metrology. In this work, we theoretically explore phase-space geometric Sagnac interferometers with trapped atomic clocks for rotation sensing, which could be intrinsically robust to certain decoherence noises and reach high precision. With the wave guide provided by sweeping ring-traps, we give criteria under which the well-known Sagnac phase is a pure or unconventional geometric phase with respect to the phase space. Furthermore, corresponding schemes for geometric Sagnac interferometers with designed sweeping angular velocity and interrogation time are presented, and the experimental feasibility is also discussed. Such geometric Sagnac interferometers are capable of saturating the ultimate precision limit given by the quantum Cramér-Rao bound.

We study the superfluidity of single component dipolar Fermi gases in three dimensions using a pairing fluctuation theory, within the context of BCS-BEC crossover. The transition temperature Tc for the dominant pz wave superfluidity exhibits a remarkable re-entrant behavior as a function of the pairing strength induced by the dipole-dipole interaction (DDI), which leads to an anisotropic pair dispersion. The anisotropy and the long range nature of the DDI cause Tc to vanish for a narrow range of intermediate interaction strengths, where a pair density wave emerges as the ground state. The superfluid density and thermodynamics below Tc, along with the density profiles in a harmonic trap, are investigated as well. Implications for experiments are discussed.