News

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

A Quantum Network of Clocks

The development of precise atomic clocks has led to many scientific and technological advances that play an increasingly important role in modern society. Shared timing information constitutes a key resource for positioning and navigation with a direct correspondence between timing accuracy and precision in applications such as the Global Positioning System (GPS). By combining precision...
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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

Polaronic Model of Two-level Systems in Amorphous Solids

While two-level systems (TLSs) are ubiqitous in solid state systems, microscopic understanding of their nature remains an outstanding problem. Conflicting phenomenological models are used to describe TLSs in seemingly similar materials when probed with different experimental techniques. Specifically, bulk measurements in amorphous solids have been interpreted using the model of a tunneling atom or group...
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Tue January 1, 2013

Topologically Protected Quantum State Transfer in a Chiral Spin Liquid

Topology plays a central role in ensuring the robustness of a wide variety of physical phenomena. Notable examples range from the current-carrying edge states associated with the quantum Hall and the quantum spin Hall effects to topologically protected quantum memory and quantum logic operations. We proposed and analysed a topologically protected channel for the transfer...
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Tue January 1, 2013

Robustness of Quantum Memories Based on Majorana Zero Modes

We analyzed the rate at which quantum information encoded in zero-energy Majorana modes was lost in the presence of perturbations. We showed that information could survive for times that scale exponentially with the size of the chain both in the presence of quenching and time-dependent quadratic dephasing perturbations, even when the latter had spectral components...
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Tue January 1, 2013

Realizing Fractional Chern Insulators in Dipolar Spin Systems

Strongly correlated quantum systems can exhibit exotic behavior controlled by topology. We predicted that the v = 1/2 fractional Chern insulator arose naturally in a two-dimensional array of driven, dipolar interacting spins. As a specific implementation, we analyzed how to prepare and detect synthetic gauge potentials for the rotational excitations of ultracold polar molecules trapped...
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Tue January 1, 2013

Collectively Enhanced Interactions in Solid-state Spin Qubits

We proposed and analyzed a technique to collectively enhance interactions between solid-state quantum registers composed from random networks of spin qubits. In such systems, disordered dipolar interactions generically result in localization. In our study, we demonstrated the emergence of a single collective delocalized eigenmode as one turned on a transverse field. The interaction strength between...
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Tue January 1, 2013

Unconventional Magnetism via Optical Pumping of Interacting Spin Systems

We considered strongly interacting systems of effective spins, subject to dissipative spin-flip processes associated with optical pumping. We predicted the existence of novel magnetic phases in the steady state of that system, which emerged due to the competition between coherent and dissipative processes. Specifically, for strongly anisotropic spin-spin interactions, we found ferromagnetic, antiferromagnetic, spin-densitywave, and...
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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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