5 research outputs found
Calibration of Spin-Light Coupling by Coherently Induced Faraday Rotation
Calibrating the strength of the light-matter interaction is an important
experimental task in quantum information and quantum state engineering
protocols. The strength of the off-resonant light-matter interaction in
multi-atom spin oscillators can be characterized by the coupling rate
. Here we utilize the Coherently Induced Faraday Rotation
(CIFAR) signal for determining the coupling rate. The method is suited for both
continuous and pulsed readout of the spin oscillator, relying only on applying
a known polarization modulation to the probe laser beam and detecting a known
optical polarization component. Importantly, the method does not require
changes to the optical and magnetic fields performing the state preparation and
probing. The CIFAR signal is also independent of the probe beam photo-detection
quantum efficiency, and allows direct extraction of other parameters of the
interaction, such as the tensor coupling , and the damping rate
. We verify this method in the continuous wave regime, probing
a strongly coupled spin oscillator prepared in a warm cesium atomic vapour.Comment: 15 pages, 6 figure
Entanglement between Distant Macroscopic Mechanical and Spin Systems
Entanglement is a vital property of multipartite quantum systems,
characterised by the inseparability of quantum states of objects regardless of
their spatial separation. Generation of entanglement between increasingly
macroscopic and disparate systems is an ongoing effort in quantum science which
enables hybrid quantum networks, quantum-enhanced sensing, and probing the
fundamental limits of quantum theory. The disparity of hybrid systems and the
vulnerability of quantum correlations have thus far hampered the generation of
macroscopic hybrid entanglement. Here we demonstrate, for the first time,
generation of an entangled state between the motion of a macroscopic mechanical
oscillator and a collective atomic spin oscillator, as witnessed by an
Einstein-Podolsky-Rosen variance below the separability limit, . The mechanical oscillator is a millimeter-size dielectric membrane and
the spin oscillator is an ensemble of atoms in a magnetic field. Light
propagating through the two spatially separated systems generates entanglement
due to the collective spin playing the role of an effective negative-mass
reference frame and providing, under ideal circumstances, a backaction-free
subspace; in the experiment, quantum backaction is suppressed by 4.6 dB. Our
results pave the road towards measurement of motion beyond the standard quantum
limits of sensitivity with applications in force, acceleration,and
gravitational wave detection, as well as towards teleportation-based protocols
in hybrid quantum networks.Comment: 24 pages, 12 figure