News: Research Highlights

Tue January 1, 2013

Keldysh Approach for Non-equilibrium Phase Transitions in Quantum Optics: Beyond the Dicke Model in Optical Cavities

We investigated nonequilibrium phase transitions for driven atomic ensembles interacting with a cavity mode and coupled to a Markovian dissipative bath. In the thermodynamic limit and at low frequencies, we showed that the distribution function of the photonic mode was thermal, with an effective temperature set by the atom-photon interaction strength. That behavior characterized the...
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Tue January 1, 2013

Dressed-State Resonant Coupling between Bright and Dark Spins in Diamond

A critical ingredient for quantum control of atom-like and hybrid systems is a better understanding of decoherence as well as the control of many-body quantum dynamics.
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Tue January 1, 2013

Many-body Localization with Dipoles

Systems of strongly interacting dipoles offer an attractive platform to study many-body localized phases, owing to their long coherence times and strong interactions. We explored conditions under which such localized phases persisted in the presence of power-law interactions and supplemented our analytic treatment with numerical evidence of localized states in one dimension. We proposed several...
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Tue January 1, 2013

Heisenberg-limited Atom Clocks based on Entangled Qubits

We presented a quantum-enhanced atomic clock protocol based on groups of sequentially larger Greenberger-Horne-Zeilinger (GHZ) states, which achieved the best clock stability allowed by quantum theory up to a logarithmic correction. The simultaneous interrogation of the laser phase with such a cascade of GHZ states realized an incoherent version of the phase estimation algorithm that...
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Tue January 1, 2013

Pauli Paramagnetism of an Ideal Fermi Gas

Using the two lowest hyperfine states of a non-interacting ultracold Fermi gas of 6Li as pseudospin states, we have measured the magnetic susceptibility of such a system as a demonstration of the textbook physics of Pauli paramagnetism [1]. An imbalanced spin mixture of 6Li is trapped in the harmonic confinement potential at the focus of...
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Tue January 1, 2013

All-Optical Switch and Transistor Gated by One Stored Photon

In this paper we demonstrate an all-optical switch gated by one stored photon. Using an atomic ensemble trapped inside an optical cavity, we store a photon incident transverse to the cavity in the atomic ensemble, thereby changing the state of one atom. This atom then blocks the cavity for photons incident along the cavity axis....
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Tue January 1, 2013

Probing Real-space and Time Resolved Correlation Functions with Many-body Ramsey Interferometry

We proposed to use Ramsey interferometry and single-site addressability, available in synthetic matter such as cold atoms or trapped ions, to measure real-space and time-resolved spin correlation functions. Those correlation functions directly probed the excitations of the system, which made it possible to characterize the underlying many-body states. Moreover, they contained valuable information about phase...
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Tue January 1, 2013

Targeted Delivery of Nanodiamonds into Living Cells

Techniques developed in AMO physics has long served as foundations for various imaging modalities in chemistry and biology. Magnetic resonance imaging (MRI) is one such example: through the mapping of proton nuclear spin resonances under the magnetic field gradient, MRI enables both structural and functional imaging of our bodies in an unprecedented detail. Magnetometry using...
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Tue January 1, 2013

Coupling of a Single Trapped Atom to a Nanoscale Optical Cavity

In this paper in collaboration with the Lukin group, we demonstrate for the first time deterministic coupling of a trapped atom to a nanophotonic resonator. For details see Lukin’s report.
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Tue January 1, 2013

Enhanced Anti-ferromagnetic Exchange between Magnetic Impurities in a Superconducting Host

It is generally believed that superconductivity only weakly affects the indirect exchange between magnetic impurities. If the distance r between impurities is smaller than the superconducting coherence length (), this exchange is thought to be dominated by RKKY interactions, identical to those in a normal metallic host. This perception is based on a perturbative treatment...
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