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Commensurate and incommensurate 1D interacting quantum systems

Thu, 11 Jan 2024 00:00:00 +0000

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Nat Communications 15, 474 (2024).

Abstract

We use dynamically varying microscopic light potentials in a quantum-gas microscope to study commensurate and incommensurate 1D systems of interacting bosonic atoms in an optical lattice. Such incommensurate systems are analogous to doped insulating states that exhibit atom transport and compressibility. Initially, a commensurate system with unit filling and fixed atom number is prepared between two potential barriers. We deterministically create an incommensurate system by dynamically changing the position of the barriers such that the number of available lattice sites is reduced while retaining the atom number. Our commensurate and incommensurate systems are characterised by measuring the distribution of particles and holes as a function of the lattice filling, and interaction strength, and we probe the particle mobility by applying a bias potential. Our work provides the foundation for preparation of low-entropy states with controlled filling in optical lattice experiments.

Comparison of deconvolution techniques

Sun, 16 Jul 2023 00:00:00 +0000

Motivation

To understand the limits of single-atom imaging compare the effectiveness of three different deconvolution techniques that are commonly used to process the fluorescence images. We use simulated images to determine the fidelity of detecting single atoms in an optical lattice in the presence of noise, inhomogeneous fluorescence, for parameter regimes relevant to other quantum-gas microscope experiments.

Example for growing excitation modes

A wave packet, which is initially centred at zero momentum, quickly spreads over the complete Brillouin zone due to interactions and periodic driving. Those instabilities make quantum simulation experiments challenging.

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New J. Phys. 25, 083036 (2023).

Experimental setup

Abstract

Quantum-gas microscopes are used to study ultracold atoms in optical lattices at the singleparticle level. In these systems atoms are localised on lattice sites with separations close to or below the diffraction limit. To determine the lattice occupation with high fidelity, a deconvolution of the images is often required. We compare three different techniques, a local iterative deconvolution algorithm, Wiener deconvolution and the Lucy-Richardson algorithm, using simulated microscope images. We investigate how the reconstruction fidelity scales with varying signal-to-noise ratio, lattice filling fraction, varying fluorescence levels per atom, and imaging resolution. The results of this study identify the limits of singe-atom detection and provide quantitative fidelities which are applicable for different atomic species and quantum-gas microscope setups.

Accurate holographic light potentials using pixel crosstalk modelling

Fri, 24 Feb 2023 00:00:00 +0000

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Scientific Reports 13, 3252 (2023).

Abstract

Microwave preparation of two-dimensional fermionic spin mixtures

Wed, 02 Jan 2019 00:00:00 +0000

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New J. Phys. 21 013020 (2010).

Abstract

We present a method for preparing a single two-dimensional sample of a two-spin mixture of fermionic potassium in a single antinode of an optical lattice, in a quantum-gas microscope apparatus. Our technique relies on spatially-selective microwave transitions in a magnetic field gradient. Adiabatic transfer pulses were optimized for high efficiency and minimal atom loss and heating due to spin-changing collisions. We have measured the dynamics of those loss processes, which are more pronounced in the presence of a spin mixture. As the efficient preparation of atoms in a single antinode requires a homogeneous transverse magnetic field, we developed a method to image and minimize the magnetic field gradients in the focal plane of the microscope.

Sub-Doppler laser cooling of 40K

Wed, 12 Apr 2017 00:00:00 +0000

Abstract

Gray molasses is a powerful tool for sub-Doppler laser cooling of atoms to low temperatures. For alkaline atoms, this technique is commonly implemented with cooling lasers which are blue-detuned from either the D1 or D2 line. Here we show that efficient gray molasses can be implemented on the D2 line of 40K with red-detuned lasers. We obtained temperatures of $48(2),\mu {\rm{K}}$, which enables direct loading of $9.2(3)\times {10}^{6}$ atoms from a magneto-optical trap into an optical dipole trap. We support our findings by a one-dimensional model and three-dimensional numerical simulations of the optical Bloch equations which qualitatively reproduce the experimentally observed cooling effects.

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J. Phys. B: At. Mol. Opt. Phys. 50 095002 (2017).

Single-atom imaging of fermions in a quantum-gas microscope

Mon, 13 Jul 2015 00:00:00 +0000

Abstract

Single-atom-resolved detection in optical lattices using quantum-gas microscopes has enabled a new generation of experiments in the field of quantum simulation. Although such devices have been realized with bosonic species, a fermionic quantum-gas microscope has remained elusive. Here we demonstrate single-site- and single-atom-resolved fluorescence imaging of fermionic potassium-40 atoms in a quantum-gas microscope set-up, using electromagnetically-induced-transparency cooling. We detected on average 1,000 fluorescence photons from a single atom within 1.5 s, while keeping it close to the vibrational ground state of the optical lattice. A quantum simulator for fermions with single-particle access will be an excellent test bed to investigate phenomena and properties of strongly correlated fermionic quantum systems, allowing direct measurement of ordered quantum phases and out-of-equilibrium dynamics with access to quantities ranging from spin–spin correlation functions to many-particle entanglement12.

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Nature Physics 11, 738–742 (2015.