Periodic Reporting for period 1 - DAALI (Disruptive Approaches to Atom-Light Interfaces)
Berichtszeitraum: 2020-10-01 bis 2021-09-30
Realizing an efficient, controllable interface between light and atoms or atom-like emitters forms the basis of wide-ranging applications such as quantum memories for light, single-photon-level nonlinear optics, and metrology. However, significant advances are still needed to make such interfaces technologically realistic on a large scale. To this end, DAALI aims to close these gaps by developing novel disruptive platforms based on the interface of atomic media and micro- and nano-photonic systems, and exploiting powerful new paradigms for atom-light interactions. These include nonlinear optics based on strong Rydberg atom-atom interactions, exploiting the rich properties arising from atom-light interactions at the nanoscale, and the “selective radiance” arising from strong interference of light emission in sub-wavelength ordered atomic arrays.
The main work and results achieved until M12 include:
- We aim to realize the first integrated setup involving cold atoms and photonic crystal waveguides in Europe, and which exceeds previous demonstrations in key performance parameters such as number of coupled atoms and per-atom coupling efficiency. To this end, we have designed compatible photonic crystal waveguides for efficient coupling and atom trapping based on the promising photonics material of GaInP, created an open and user-friendly numerical package (Nanotrappy) to assist in the design process (such as in the calculation of trapping potentials near nanostructures), and have been developing a commercial turn-key laser system to integrate with the setup.
- We are pursuing a new approach to integrate solid-state emitters, in the form of rare-earth ions, to optical nanofibers, with the ultimate aim of demonstrating an efficient quantum memory. A novel aspect of this approach is the use of rare earth ions protected in a molecular “cage” (chelate), to improve upon ion homogeneity, coherence times, and strength of light-matter interactions. In particular, the tailored chelate in principle allows one to minimize typical problems associated with the solid-state environment, and to apply monolayers directly to the surface of nanofibers to ensure maximal coupling to the guided modes. We have already designed and synthesized the chelates, and integrated them with nanofibers. In-vacuum measurements reach record high lifetimes of 0.9ms indicating the high quantum yield of the ions and suppression of non-radiative decay channels.
- Progress in the construction of a new cold strontium atom platform. This setup will enable the generation of a defect-free 2D array with sub-wavelength lattice constant, for use in quantum optics protocols based on selective radiance.
- Realization of single-atom trapping near a whispering gallery mode resonator, with approximately 2ms lifetime. This long-lived trap is an important step in being able to realize more complex, multi-step quantum optics protocols.
- Theoretical proposal for a highly efficient photon-photon gate based on selective radiance in a 2D Rydberg array.
- Theoretical explanation for the maximum refractive index of a disordered atomic medium.
- While there has been a vast body of work on quantum nonlinear optics using Rydberg ensembles, most of this work has focused on the nonlinear response given cw input fields. Here, we have experimentally and theoretically explored the nonlinear response in the transient regimes of pulse turn-on and turn-off, and in particular have demonstrated that the turn-off regime can exhibit significantly stronger anti-bunching correlations than cw fields under certain conditions.
- We have performed experiments that advance the use of Rydberg systems in quantum nodes, by optimizing Rydberg ensembles as on-demand quantum light sources, and demonstrating low-noise storage of on-demand single photons emitted by a Rydberg ensemble into a different cold atomic ensemble.
- We have developed efficient numerical codes to calculate the linear optical response of atomic ensembles with up to N~700,000 atoms at a microscopic level. This code fully accounts for the granularity of atoms and the associated multiple scattering of light and dipole-dipole interactions, paving the way to understand the interplay between microscopic and macroscopic optical response in a wide variety of circumstances.
- Theoretical proposal and experimental demonstration of a method to efficiently and reversibly excite optical spin waves in atomic ensembles with phase-mismatched wavevectors relative to the dispersion relation of light. Future application of this technique to arrays should allow access to exotic, highly subradiant modes of such a system.
- Construction of an upgraded microtoroid cavity QED setup, designed to support single-atom trapping. The goal is to use this system to achieve atom-photon and photon-photon gates that for the first time simultaneously demonstrate high fidelity and photon survival probability.
- Improved experimental demonstration of the “atomic mirror” phenomenon in an atom-nanofiber setup, involving N~3000 atoms. With atoms trapped at a lattice constant nearly commensurate with the atomic wavelength, up to 75% reflection of resonant light by the atomic array has been observed, to utilize the phenomenon for single-photon-level nonlinear optics.
- We aim to realize the first integrated setup involving cold atoms and photonic crystal waveguides in Europe, and which exceeds previous demonstrations in key performance parameters such as number of coupled atoms and per-atom coupling efficiency. To this end, we have designed compatible photonic crystal waveguides for efficient coupling and atom trapping based on the promising photonics material of GaInP, created an open and user-friendly numerical package (Nanotrappy) to assist in the design process (such as in the calculation of trapping potentials near nanostructures), and have been developing a commercial turn-key laser system to integrate with the setup.
- We are pursuing a new approach to integrate solid-state emitters, in the form of rare-earth ions, to optical nanofibers, with the ultimate aim of demonstrating an efficient quantum memory. A novel aspect of this approach is the use of rare earth ions protected in a molecular “cage” (chelate), to improve upon ion homogeneity, coherence times, and strength of light-matter interactions. In particular, the tailored chelate in principle allows one to minimize typical problems associated with the solid-state environment, and to apply monolayers directly to the surface of nanofibers to ensure maximal coupling to the guided modes. We have already designed and synthesized the chelates, and integrated them with nanofibers. In-vacuum measurements reach record high lifetimes of 0.9ms indicating the high quantum yield of the ions and suppression of non-radiative decay channels.
- Progress in the construction of a new cold strontium atom platform. This setup will enable the generation of a defect-free 2D array with sub-wavelength lattice constant, for use in quantum optics protocols based on selective radiance.
- Realization of single-atom trapping near a whispering gallery mode resonator, with approximately 2ms lifetime. This long-lived trap is an important step in being able to realize more complex, multi-step quantum optics protocols.
- Theoretical proposal for a highly efficient photon-photon gate based on selective radiance in a 2D Rydberg array.
- Theoretical explanation for the maximum refractive index of a disordered atomic medium.
- While there has been a vast body of work on quantum nonlinear optics using Rydberg ensembles, most of this work has focused on the nonlinear response given cw input fields. Here, we have experimentally and theoretically explored the nonlinear response in the transient regimes of pulse turn-on and turn-off, and in particular have demonstrated that the turn-off regime can exhibit significantly stronger anti-bunching correlations than cw fields under certain conditions.
- We have performed experiments that advance the use of Rydberg systems in quantum nodes, by optimizing Rydberg ensembles as on-demand quantum light sources, and demonstrating low-noise storage of on-demand single photons emitted by a Rydberg ensemble into a different cold atomic ensemble.
- We have developed efficient numerical codes to calculate the linear optical response of atomic ensembles with up to N~700,000 atoms at a microscopic level. This code fully accounts for the granularity of atoms and the associated multiple scattering of light and dipole-dipole interactions, paving the way to understand the interplay between microscopic and macroscopic optical response in a wide variety of circumstances.
- Theoretical proposal and experimental demonstration of a method to efficiently and reversibly excite optical spin waves in atomic ensembles with phase-mismatched wavevectors relative to the dispersion relation of light. Future application of this technique to arrays should allow access to exotic, highly subradiant modes of such a system.
- Construction of an upgraded microtoroid cavity QED setup, designed to support single-atom trapping. The goal is to use this system to achieve atom-photon and photon-photon gates that for the first time simultaneously demonstrate high fidelity and photon survival probability.
- Improved experimental demonstration of the “atomic mirror” phenomenon in an atom-nanofiber setup, involving N~3000 atoms. With atoms trapped at a lattice constant nearly commensurate with the atomic wavelength, up to 75% reflection of resonant light by the atomic array has been observed, to utilize the phenomenon for single-photon-level nonlinear optics.
Results obtained within DAALI constitute important advances beyond state of the art, and have the potential to produce significant scientific and technological impact. These include:
- Despite general agreement that interfacing cold atoms with photonic crystal waveguides constitutes an exciting new direction for quantum optics, there has only been one experimental realization thus far. One barrier is the design of photonic crystal systems that are simultaneously compatible with atom trapping and allow for strong resonant atom-light interactions. Our open, user-friendly Nanotrappy numerical package will eliminate this barrier and facilitate members of the scientific community to enter this field.
- Whispering gallery mode resonators exhibit promising figures of merit for single-atom cavity QED, such as in terms of cavity cooperativity and in/out-coupling efficiencies. However, a major limitation to their usage in quantum information processing protocols up to now has been the lack of an atom trapping mechanism, as is needed to implement more complex protocols. Our first demonstration of single-atom trapping capabilities should pave the way to the realization of atom-photon and photon-photon gates that simultaneously exhibit high fidelity and photon survival probabilities.
- Our numerical codes to simulate the microscopic linear optical dynamics of up to N~700,000 atoms go two orders of magnitude beyond comparable works in literature, in terms of system size. This should allow for better understanding of the complex interplay between microscopic and macroscopic optical response in dense atomic media, such as arising from multiple scattering of light and dipole-dipole interactions.
- Our proposed protocol for a photon-photon gate in a 2D Rydberg atomic array exhibits a significant polynomial improvement in error scaling versus Rydberg blockade radius over other known protocols. This result offers more convincing evidence that selective radiance, and strong interference of light emission in ordered arrays, constitute a powerful, untapped resource for applications based on efficient quantum atom-light interactions.
- Despite general agreement that interfacing cold atoms with photonic crystal waveguides constitutes an exciting new direction for quantum optics, there has only been one experimental realization thus far. One barrier is the design of photonic crystal systems that are simultaneously compatible with atom trapping and allow for strong resonant atom-light interactions. Our open, user-friendly Nanotrappy numerical package will eliminate this barrier and facilitate members of the scientific community to enter this field.
- Whispering gallery mode resonators exhibit promising figures of merit for single-atom cavity QED, such as in terms of cavity cooperativity and in/out-coupling efficiencies. However, a major limitation to their usage in quantum information processing protocols up to now has been the lack of an atom trapping mechanism, as is needed to implement more complex protocols. Our first demonstration of single-atom trapping capabilities should pave the way to the realization of atom-photon and photon-photon gates that simultaneously exhibit high fidelity and photon survival probabilities.
- Our numerical codes to simulate the microscopic linear optical dynamics of up to N~700,000 atoms go two orders of magnitude beyond comparable works in literature, in terms of system size. This should allow for better understanding of the complex interplay between microscopic and macroscopic optical response in dense atomic media, such as arising from multiple scattering of light and dipole-dipole interactions.
- Our proposed protocol for a photon-photon gate in a 2D Rydberg atomic array exhibits a significant polynomial improvement in error scaling versus Rydberg blockade radius over other known protocols. This result offers more convincing evidence that selective radiance, and strong interference of light emission in ordered arrays, constitute a powerful, untapped resource for applications based on efficient quantum atom-light interactions.