Quantum simulation of confinement dynamics

Quantum computers have generated much excitement over recent years due to their potential to outperform classical computers in many difficult problems. While a fully fault tolerant quantum device is yet to be built, there has been much work pushing for noisy intermediate-scale quantum (NISQ) devices to achieve quantum advantage. One of the most promising fields to accomplish this is in quantum simulation of quantum many-body systems. A classical computer is able to simulate a general quantum system but suffers from exponential memory requirements in system size. Thus, for exact results, classical computers are limited to simulating just tens of particles whereas realistic quantum systems are comprised of $\sim 10^{23}$. Quantum computers are able to reduce this memory cost to polynomial growth making them key to understand the physics of many-body systems. One area that is notably difficult to simulate is confinement physics. Confinement is the phenomenon in which the energy of two particles grows indefinitely with their separation - most prominently found between quarks in quantum chromodynamics (QCD). In this work we will consider the application of quantum devices to simulate such phenomena. In particular, we consider simple condensed matter systems, namely variations of the Ising model, that exhibit confinement physics. In the first half of this work we perform an analytical and numerical study of confinement, and develop a trotterization protocol to enable the quantum simulation of such physics on a digital quantum computer. We present results obtained directly on an IBM quantum computer showing the non-equilibrium effects of confinement in such systems. In order to achieve these results we developed state-of-the-art error mitigation methods to combat the large errors inherently faced in current NISQ devices. In the latter half, we propose physical phenomena that may act as a benchmark for quantum devices in the future. Collisions of mesons (boundstates of two particles) with impurities are considered in which a long-lived metastable state is found to form. Such collisions have potential to be simulated on digital quantum computers in the near future. We then consider collisions of mesons in systems with long-range interactions. We show how collisions of interacting mesons can lead to the formation of hadrons (boundstates of many constituent particles) in a fusion type event. While these proposals are beyond current digital quantum computer capabilities, analogue quantum simulation devices such as trapped ion setups or Rydberg atom experiments are well suited to realise this physics.Open Acces

Quantum many-body scars in optical lattices

The concept of quantum many-body scars has recently been put forward as a route to describe weak ergodicity breaking and violation of the eigenstate thermalization hypothesis. We propose a simple setup to generate quantum many-body scars in a doubly modulated Bose-Hubbard system which can be readily implemented in cold atomic gases. The dynamics are shown to be governed by kinetic constraints which appear via density-assisted tunneling in a high-frequency expansion. We find the optimal driving parameters for the kinetically constrained hopping which leads to small isolated subspaces of scared eigenstates. The experimental signatures and the transition to fully thermalizing behavior as a function of driving frequency are analyzed

Experimental realization of a thermal squeezed state of levitated optomechanics

We experimentally squeeze the thermal motional state of an optically levitated nanosphere by fast switching between two trapping frequencies. The measured phase-space distribution of the center of mass of our particle shows the typical shape of a squeezed thermal state, from which we infer up to 2.7 dB of squeezing along one motional direction. In these experiments the average thermal occupancy is high and, even after squeezing, the motional state remains in the remit of classical statistical mechanics. Nevertheless, we argue that the manipulation scheme described here could be used to achieve squeezing in the quantum regime if preceded by cooling of the levitated mechanical oscillator. Additionally, a higher degree of squeezing could, in principle, be achieved by repeating the frequency-switching protocol multiple times

Magneto-optical trapping in a near-surface borehole

Borehole gravity sensing can be used in a number of applications to measure features around a well including rock-type change mapping and determination of reservoir porosity. Quantum technology gravity sensors based on atom interferometry have the ability to offer increased survey speeds and reduced need for calibration. While surface sensors have been demonstrated in real world environments, significant improvements in robustness and reductions to radial size, weight, and power consumption are required for such devices to be deployed in boreholes. To realise the first step towards the deployment of cold atom-based sensors down boreholes, we demonstrate a borehole-deployable magneto-optical trap, the core package of many cold atom-based systems. The enclosure containing the magneto-optical trap itself had an outer radius of ($60\pm0.1$) mm at its widest point and a length of ($890\pm5$) mm. This system was used to generate atom clouds at 1 m intervals in a 14 cm wide, 50 m deep borehole, to simulate an in-borehole gravity surveys are performed. During the survey the system generated on average clouds of (3.0 $\pm 0.1) \times 10^{5}$ $^{87}$Rb atoms with the standard deviation in atom number across the survey observed to be as low as $9 \times 10^{4}$

Magneto-optical trapping in a near-suface borehole

Borehole gravity sensing can be used in a number of applications to measure features around a well, including rock-type change mapping and determination of reservoir porosity. Quantum technology gravity sensors, based on atom interferometry, have the ability to offer increased survey speeds and reduced need for calibration. While surface sensors have been demonstrated in real world environments, significant improvements in robustness and reductions to radial size, weight, and power consumption are required for such devices to be deployed in boreholes. To realise the first step towards the deployment of cold atom-based sensors down boreholes, we demonstrate a borehole-deployable magneto-optical trap, the core package of many cold atom-based systems. The enclosure containing the magneto-optical trap itself had an outer radius of (60 ± 0.1) mm at its widest point and a length of (890 ± 5) mm. This system was used to generate atom clouds at 1 m intervals in a 14 cm wide, 50 m deep borehole, to simulate how in-borehole gravity surveys are performed. During the survey, the system generated, on average, clouds of (3.0 ± 0.1) × 105 87Rb atoms with the standard deviation in atom number across the survey observed to be as low as 8.9 × 104

Additive manufacturing of magnetic shielding and ultra-high vacuum flange for cold atom sensors

Abstract Recent advances in the understanding and control of quantum technologies, such as those based on cold atoms, have resulted in devices with extraordinary metrological performance. To realise this potential outside of a lab environment the size, weight and power consumption need to be reduced. Here we demonstrate the use of laser powder bed fusion, an additive manufacturing technique, as a production technique relevant to the manufacture of quantum sensors. As a demonstration we have constructed two key components using additive manufacturing, namely magnetic shielding and vacuum chambers. The initial prototypes for magnetic shields show shielding factors within a factor of 3 of conventional approaches. The vacuum demonstrator device shows that 3D-printed titanium structures are suitable for use as vacuum chambers, with the test system reaching base pressures of 5 ± 0.5 × 10−10 mbar. These demonstrations show considerable promise for the use of additive manufacturing for cold atom based quantum technologies, in future enabling improved integrated structures, allowing for the reduction in size, weight and assembly complexity