48 research outputs found
Quantum nonlinear optics with single photons enabled by strongly interacting atoms
Get PDFThe realization of strong nonlinear interactions between individual light quanta (photons) is a long-standing goal in optical science and engineering, being of both fundamental and technological significance. In conventional optical materials, the nonlinearity at light powers corresponding to single photons is negligibly weak. Here we demonstrate a medium that is nonlinear at the level of individual quanta, exhibiting strong absorption of photon pairs while remaining transparent to single photons. The quantum nonlinearity is obtained by coherently coupling slowly propagating photons to strongly interacting atomic Rydberg states in a cold, dense atomic gas. Our approach paves the way for quantum-by-quantum control of light fields, including single-photon switching, all-optical deterministic quantum logic and the realization of strongly correlated many-body states of light.National Science Foundation (U.S.)MIT-Harvard Center for Ultracold AtomsUnited States. Air Force Office of Scientific Research. Multidisciplinary University Research Initiative (Quantum Memories
Storing single photons in broadband vapor cell quantum memories
Get PDFSingle photons are an essential resource for realizing quantum technologies. Together with compatible quantum memories granting control over when a photon arrives, they form a foundational component both of quantum communication and quantum information processing. Quality solid-state single photon sources deliver on the high bandwidths and rates required for scalable quantum technology, but require memories that match these operational parameters. In this thesis, I report on quantum memories based on electromagnetically induced transparency and built in warm rubidium vapor, with such fast and high bandwidth interfaces in mind. I also present work on a heralded single photon source based on parametric downconversion in an optical cavity, operated in a bandwidth regime of a few 100s of megahertz. The systems are characterized on their own and together in a functional interface. As the photon generation process is spontaneous, the memory is implemented as a fully reactive device, capable of storing and retrieving photons in response to an asynchronous external trigger.
The combined system is used to demonstrate the storage and retrieval of single photons in and from the quantum memory. Using polarization selection rules in the Zeeman substructure of the atoms, the read-out noise of the memory is considerably reduced from what is common in ground-state storage schemes in warm vapor. Critically, the quantum signature in the photon number statistics of the retrieved photons is successfully maintained, proving that the emission from the memory is dominated by single photons. We observe a retrieved single-photon state accuracy of for short storage times, which remains throughout the memory lifetime of ns. The end-to-end efficiency of the memory interfaced with the photon source is , which will be further improved in the future by optimizing the operating regime. With its operation bandwidth of MHz, our system opens up new possibilities for single-photon synchronization and local quantum networking experiments at high repetition rates
Light storage for one second in room-temperature alkali vapor
No full textAbstractLight storage, the controlled and reversible mapping of photons onto long-lived states of matter, enables memory capability in optical quantum networks. Prominent storage media are warm alkali vapors due to their strong optical coupling and long-lived spin states. In a dense gas, the random atomic collisions dominate the lifetime of the spin coherence, limiting the storage time to a few milliseconds. Here we present and experimentally demonstrate a storage scheme that is insensitive to spin-exchange collisions, thus enabling long storage times at high atomic densities. This unique property is achieved by mapping the light field onto spin orientation within a decoherence-free subspace of spin states. We report on a record storage time of 1 s in room-temperature cesium vapor, a 100-fold improvement over existing storage schemes. Furthermore, our scheme lays the foundations for hour-long quantum memories using rare-gas nuclear spins.</jats:p
Fast, noise-free atomic optical memory with 35% end-to-end efficiency
Get PDFCoherent optical memories will likely play an important role in future
quantum communication networks. Among the different platforms, memories based
on ladder-type orbital transitions in atomic gasses offer high bandwidth
( MHz), continuous (on-demand) readout, and low-noise operation. Here we
report on an upgraded setup of our previously-reported fast ladder memory, with
improved efficiency and lifetime, and reduced noise. The upgrade employs a
stronger control field, wider signal beam, reduced atomic density, higher
optical depth, annular optical-pumping beam, and weak dressing of an auxiliary
orbital to counteract residual Doppler-broadening. For a 2 ns-long pulse, we
demonstrate 53% internal efficiency, 35% end-to-end efficiency, noise photons per pulse, and a lifetime of 108 ns. This
combination of performances is a record for continuous-readout memories
Nonlinear quantum optics mediated by Rydberg interactions
Get PDFBy mapping the strong interaction between Rydberg excitations in ultra-cold atomic ensembles onto single photons via electromagnetically induced transparency, it is now possible to realize a medium which exhibits a strong optical nonlinearity at the level of individual photons. We review the theoretical concepts and the experimental state-of-the-art of this exciting new field, and discuss first applications in the field of all-optical quantum information processing
Strong coupling of alkali spins to noble-gas spins with hour-long coherence time
No full textNuclear spins of noble gases can maintain coherence for hours at ambient
conditions owing to their extraordinary isolation by the enclosing, complete
electronic shells. This isolation, however, impedes the ability to manipulate
and control them by optical means or by physical coupling to other spin gases.
Here we experimentally achieve strong coherent coupling between noble-gas spins
and the optically-accessible spins of alkali-metal vapor. Stochastic
spin-exchange collisions, underlying the coupling, accumulate to a coherent
periodic exchange of spin excitations between the two gases. We obtain a
coupling rate 10 times higher than the decay rate, observe the resultant
avoided crossing in the spectral response of the spins, and demonstrate the
external control over the coupling by magnetic fields. These results open a
route for efficient and rapid interfacing with noble-gas spins for applications
in quantum sensing and information
<i>Colloquium</i> : Strongly interacting photons in one-dimensional continuum
No full textPhoton-photon scattering in vacuum is extremely weak. However, strong effective interactions between single photons can be realized by employing strong light-matter coupling. These interactions are a fundamental building block for quantum optics, bringing many-body physics to the photonic world and providing important resources for quantum photonic devices and for optical metrology. This Colloquium reviews the physics of strongly interacting photons in one-dimensional systems with no optical confinement along the propagation direction. It focuses on two recently demonstrated experimental realizations: superconducting qubits coupled to open transmission lines and interacting Rydberg atoms in a cold gas. Advancements in the theoretical understanding of these systems are presented in complementary formalisms and compared to experimental results. The experimental achievements are summarized alongside a description of the quantum optical effects and quantum devices emerging from them
