News

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...

News type: Research Highlights

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...

News type: Research Highlights

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...

News type: Research Highlights

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...

News type: Research Highlights

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...

News type: Research Highlights

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...

News type: Research Highlights

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...

News type: Research Highlights

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...

News type: Research Highlights

Tue, January 1, 2013

Attractive Photons in a Quantum Nonlinear Medium

In this paper, we demonstrate for the first time a bound state of two photons. We illuminate a dense and cold atomic ensemble with weak laser light underconditions of electromagnetically induced transparency to an atomic Rydberg state. When we detune the control laser coupling the unstable intermediate state to the Rydberg level, the probe photons...

News type: Research Highlights

Tue, January 1, 2013

All-optical Sensing of a Single-molecule Electron Spin

We demonstrated an all-optical method for magnetic sensing of individual molecules in ambient conditions at room temperature. Our approach was based on shallow nitrogen-vacancy (NV) centers near the surface of a diamond crystal, which we used to detect single paramagnetic molecules covalently attached to the diamond surface. The manipulation and readout of the NV centers...

News type: Research Highlights