Research - Ultracold Fermi Gases @ Technion

Understanding the physics of many interacting quantum particles is a formidable task due to the exponential growth of classical computational complexity with particle number. However, R. Feynman pointed out the solution: employing a quantum computer or simulator [1]. Our research is dedicated to comprehending complex collective quantum phenomena through experiments with an ensemble of ultracold neutral atoms—a system that offers exceptional cleanliness and precise control. The questions we address in these experiments have broad relevance and significance across a wide range of energy scales [2], encompassing electrons in metals, holes in superconductors, spins in magnets, and even protons and neutrons in neutron stars.

We have two labs in which we follow complementary research routes utilizing top-down and bottom-up approaches. The essence of the top-down approach is to gradually bring the atomic ensemble towards its quantum ground state. Starting from a gas at room temperature, we employ a combination of laser cooling and forced evaporation techniques to reduce the gas temperature to the nano Kelvin regime, where quantum effects dominate. By tuning inter-particle interactions using an external magnetic field and leveraging light and magnetic field gradients, we engineer the Hamiltonian governing the system. In this setting, we investigate both the equilibrium properties and the dynamics of an excited gas. Our apparatus is built with a fermionic isotope of potassium (⁴⁰K), enabling quantum simulations of fermionic particles such as electrons, protons, and neutrons. Over the last couple of years, we have studied the normal phase of a spin-balanced gas, the polaron-molecule quantum phase transition in a spin-imbalanced gas, and the formation of superfluidity in a Fermi gas driven by an external periodic force. We have developed unique detection methods, utilizing fluorescence-based spectroscopy and Raman transitions, that allow us to probe directly the excitation spectrum of quasi-particles.

In the bottom-up approach, we trap and manipulate atoms independently to construct quantum states one by one. This approach offers greater power and flexibility compared to the top-down approach but is accompanied by significant technological challenges. We employ microscopic optical beams, known as optical tweezers, to trap single fermionic atoms. These atoms can store quantum information in their internal states, serving as qubits for quantum computation [3]. Additionally, we can arrange traps in various arrays and geometries, enabling the realization of a wide range of model Hamiltonians that are inaccessible in other systems. An atom array based on optical tweezers is considered a leading path towards quantum computation and simulation. We are particularly interested in employing tunneling and

In our bottom-up approach, we employ precise trapping and manipulation techniques to individually construct quantum states atom by atom. This method offers enhanced power and flexibility compared to the top-down approach, although it presents notable technological challenges. To trap single fermionic atoms, we utilize microscopic optical beams called optical tweezers. These highly focused beams allow us to confine and control individual atoms. Trapped atoms have the ability to store quantum information within their internal states, effectively serving as qubits for quantum computation [3]. The utilization of an atom array based on optical tweezers represents a leading pathway towards quantum computation and simulation. We are particularly intrigued by the prospects of implementing quantum gates using tunneling and exchange interactions within this setup. Furthermore, we have the capability to arrange these traps in various arrays and geometries, enabling the realization of a wide range of model Hamiltonians that are inaccessible in other systems. In addition to quantum computation, we are also exploring the application of fermions trapped in optical tweezers for precision force and acceleration metrology.

[1] P. Feynman, “Simulating physics with computers”, International journal of theoretical physics 21, 467–488(1982).

[2] Bloch, J. Dalibard, and W. Zwerger, “Many-body physics with ultracold gases”, Rev. Mod. Phys. 80, 885–964 (2008).

[3] L. Henriet, L. Beguin, A. Signoles, T. Lahaye, A. Browaeys, G.-O. Reymond, and C. Jurczak, “Quantum computing with neutral atoms”, Quantum 4, 327 (2020).

Here are introductions to some of our past research subjects: