Atom Qubit Array (AQuA) Experiment

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In the AQuA lab we are exploring gate-based quantum computing with arrays of neutral Cs atoms and Rydberg interactions. Near term project directions include two qubit gates with one-photon Rydberg transitions and an upgrade of the computer to a dual-species architecture with Rb and Cs.

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Some relevant publications:

• T. M. Graham, L. Phuttitarn, R. Chinnarasu, et. al. Midcircuit Measurements on a Single-Species Neutral Alkali Atom Quantum Processor, Phys. Rev. X 13, 041051 (2023). https://doi.org/10.1103/PhysRevX.13.041051
• Graham, T.M., Song, Y., Scott, J. et al. Multi-qubit entanglement and algorithms on a neutral-atom quantum computer. Nature 604, 457–462 (2022). https://doi.org/10.1038/s41586-022-04603-6
• T. M. Graham, M. Kwon, B. Grinkemeyer, et. al. Rydberg-Mediated Entanglement in a Two-Dimensional Neutral Atom Qubit Array, Phys. Rev. Lett. 123, 230501 (2019). https://doi.org/10.1103/PhysRevLett.123.230501

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Meet the team:

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Neutral atom quantum processor with local addressing beams:

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Results in the AQuA lab as of Summer 2024:

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Sensing and Networking with Atomic Qubits (SNAQ) Experiment

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Quantum networks are of interest both in terms of both fundamental science and for growing the quantum ecosystem, such as providing a pathway to scaling quantum computers. In the SNAQ lab we are working towards remote entanglement generation between individual atoms in separate vacuum chambers, where the atoms can be either the same species, Rb, or two different atomic species Rb and Cs. The distributed entanglement can then be used as a resource for enhanced quantum sensing with entangled states, or for linking up quantum registers implemented with atom arrays at each network node.

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Relevant publications:

• Omar Nagib, P. Huft, A. Safari, and M. Saffman, Robust atom-photon gate for quantum information processing, Phys. Rev. A 109, 032602 (2024) https://doi.org/10.1103/PhysRevA.109.032602
• Young, C.B., Safari, A., Huft, P. et al. "An architecture for quantum networking of neutral atom processors." Appl. Phys. B 128, 151 (2022). https://doi.org/10.1007/s00340-022-07865-0
• P. Huft, Y. Song, T. M. Graham, K. Jooya, S. Deshpande, C. Fang, M. Kats, and M. Saffman, "Simple, passive design for large optical trap arrays for single atoms" Phys. Rev. A 105, 063111 (2022). https://doi.org/10.1103/PhysRevA.105.063111

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Meet the team:

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A network of quantum registers with parabolic mirrors for communication qubit photon collection:

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Results in the SNAQ lab as of Summer 2024:

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Our two node apparatus in the lab:
We have pioneered the design of network nodes with "integrated" mm- and cm-scale optics, bringing light into and out of the vacuum chamber through optical fibers. This reduces the experimental footprint and can improve mechanical stability, as the optical alignment is permananent.

The integrated optical chips in nodes "Alice" and "Bob":

Additionally, we have demonstrated the first use of a parabolic mirror with neutral atoms for simultaneous trapping and photon collection.

Schematic of the node geometry showing dipole trap photon collection, and photon collection data from singles atom trapped at the focus of the parabolic mirror:

A MOT in Node 1 ("Alice") and a histogram of photons collected by the SPCM, indicating single atom loading:

Cesium Lattice Optical Clock (CLOC) Experiment

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In the CLOC lab we are working on creating an optical lattice clock with Cs atoms addressed on a forbidden optical transition, with atoms confined in a 3D optical lattice using a magic trap wavelength. By using the forbidden transition at 685 nm, we can achieve colder atoms compared to using the typical D2 cycling transition due to the narrow linewidth of the transition. Moreover, this transition allows us to do background-free imaging, where the emitted light as at 852 nm light, and the 685 nm imaging light can be filtered out.

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Some relevant publications:

• A. Sharma, S. Kolkowitz, M. Saffman, Analysis of a Cesium lattice optical clock, arXiv:2203.08708, https://doi.org/10.48550/arXiv.2203.08708
• P. Huft, Y. Song, T. M. Graham, K. Jooya, S. Deshpande, C. Fang, M. Kats, and M. Saffman, "Simple, passive design for large optical trap arrays for single atoms" Phys. Rev. A 105, 063111 (2022). https://doi.org/10.1103/PhysRevA.105.063111

Meet the team:

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Results in the CLOC lab as of Summer 2024:

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Single Cs atoms trapped in a blue-detuned trap array formed with passive optics:

685nm MOT imaged by pumping only the quadrupole line. No 852nm pump light or 895nm repump light was used:

Old Projects

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We are exploring the use of neutral atoms for quantum information processing using several related but complementary approaches. Experiments have been conducted using three different atomic species: Rb, Cs, and Ho.

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Rb: Rydberg blockade for atom-atom and atom-photon entanglement

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Cs: single atom qubit array

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Cs: holographic atom traps

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Ho: laser cooling and collective encoding

Pattern formation in intracavity second harmonic generation

MPEG movie showing the formation of a hexagonal pattern in singly resonant SHG (numerical simulation).

MPEG movie of spiral wave dynamics (left) in the internally pumped Optical Parametric Oscillator (numerical simulation, caution 7 MB file). Intracavity second harmonic generation (middle) in a KNbO₃ crystal. Quantum structures in second harmonic generation can be seen by the image on the right.

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Atom Optics

Ultracold atoms propagate as waves. We are studying nonlinear effects that arise from the coupled propagation of light and matter. Predicted effects include filamentation instabilities, and soliton formation. Calculations of coupled filamentation of atomic field (left) and optical field (right).