About the Kaufman Group
How does classical physics –- such as statistical mechanics — emerge from the collective behavior of quantum mechanical systems? Can we develop new tools for the manipulation of individual particles, such as complex atoms, ions or molecules, whose interactions and internal degrees of freedom establish new prospects for quantum science?
To answer questions like these, our group applies the tools of atomic, molecular, and optical physics to the microscopic study and control of quantum systems, for applications in quantum simulation, quantum information, and metrology. We marry the tools of quantum gas microscopy, optical tweezer technology, and high precision spectroscopy in order to gain single-particle control at fundamental length scales and very small energy scales.
Towards these goals, we trap single alkaline-earth atoms in optical tweezer arrays, a powerful and effective technology that we demonstrated in 2018 for the first time. Optical tweezers allow precise single-particle control, the engineering of different forms of atomic interactions, and high-fidelity atom-resolved readout. However, while previous work with optical tweezers had focused on alkali atoms, the 2018 work opened the door to tweezer-based control of atoms with two electrons in their valence shell -- although a tiny addition, this additional electron gives rise to the rich internal structure of alkaline-earth atoms, which underlies their applications in metrology, quantum simulation, and quantum information. In this lab, we apply the microscopic control capabilities emerging from the optical tweezer toolset to the quantum science directions that emerge from the use of alkaline-earth atoms.
One of the scientific pursuits for which alkaline-earth atoms are most famous is optical atomic clocks. In atoms like Strontium and Ytterbium, there exists a long-lived optical transition known as the “clock transition”. Viewed as an oscillator, this transition has an intrinsic quality factor of in excess of 1017— that is, it can ring quadrillions of times before the oscillations die out. This means this oscillator can serve as an exceptional time-keeper, and, indeed, in the past decade, such optical atomic clocks have allowed some of the most precise measurements ever made by humans.
Another appealing aspect of alkaline-earth atoms is the presence of a second relatively narrow transition — though not as narrow as the clock transition — that can be used for ground-state laser cooling. This is especially powerful when combined with the possibility of rearranging optical tweezers to prepare arbitrary atomic distributions with very low entropy in the atomic spatial distribution. So far, large-scale demonstrations of atomic rearrangement have been used for spin models, with atoms that might be relatively hot in their motional degrees of freedom. In this project, we seek to prepare arbitrary distributions of scalable arrays of ground-state atoms for large scale itinerant models.
Unlike their bosonic counterpart, fermionic isotopes of alkaline-earth atoms benefit from having nuclear spin. This spin has been proposed for new many-body models, such as SU(N) physics, as well as the basis for new qubit architectures. In a new experiment, we seek to gain single-qubit-resolved control of arrays of Ytterbium-171 atoms, where quantum information is stored in the spin-1/2 nuclear spin of this isotope. We seek to engineer the resulting system to fully exploit the high two-qubit gate speeds possible with large Rydberg Rabi frequencies from the excited clock state.
In the Spotlight
Our first paper from the Ytterbium tweezer project has been published in PRX! We show rapid control of the nuclear-spin qubit, T1 on 10 to 100 second timescales, and T2 times of several seconds. We also harness the narrow transitions in Yb to perform near-deterministic loading and ground-state cooling. See also follow up synopsis in Physics here.
In January, we posted our first demonstration of a new concept for tweezer-programmable optical lattices. Using tweezers with spatial scale on the order of 400 nm, we can program the dynamics and Hamiltonian with single lattice site resolution. We use resolved-sideband cooling to prepare the atoms at extremely low temperatures. From these conditions, we demonstrate for the first time the implementation of a spatial search algorithm originally proposed by Childs and Goldstone. Andrew Childs collaborated with us on this project, and we expect interesting extensions down the line to multi-particle search algorithms.
In the past month, the group has put up two new preprints.
- In the strontium experiment, we report the generation of entangled Bell states, prepared in optical clock qubits, whose phase coherence persists for more than 4 seconds. This uses a gate scheme proposed by M. Martin and I. Deutsch, based on Rydberg-mediated interactions. See the preprint here.
- On the Ytterbium experiment, we report our first results preparing, controlling, and detecting arrays of nuclear spin qubits of 171Yb. We observe high fidelity control with sub-microsecond pulse times. We also demonstrate low-entropy array preparation through deterministic loading techniques via the use of narrow-line transitions and Raman-sideband cooling to near the motional ground state. See the preprint here.
This year’s Q2B (Quantum 2 Business) conference took place on December 7-9 at the Santa Clara Convention Center. Several big names spoke at the event, and it was a place to forge new partnerships and connections. For one lucky JILAn, the trip to this conference was sponsored by CUbit Quantum Initiative, (CUbit). "I am very grateful to Women in Quantum and CUbit for sponsoring me to attend the Q2B conference," Joanna Lis said. Lis is a graduate student within JILA Fellow Adam Kaufman's laboratory. "My research is looking at neutral atoms in tweezers. I was positively surprised on how much presence neutral atom platforms had within the conference," she added.