The control and manipulation of quantum systems without excitation is challenging, due to the complexities in fully modeling such systems accurately and the difficulties in controlling these inherently fragile systems experimentally. For example, while protocols to decompress Bose-Einstein condensates (BEC) faster than the adiabatic timescale (without excitation or loss) have been well developed theoretically, experimental implementations of these protocols have yet to reach speeds faster than the adiabatic timescale. In this work, we experimentally demonstrate an alternative approach based on a machine learning algorithm which makes progress towards this goal. The algorithm is given control of the coupled decompression and transport of a metastable helium condensate, with its performance determined after each experimental iteration by measuring the excitations of the resultant BEC. After each iteration the algorithm adjusts its internal model of the system to create an improved control output for the next iteration. Given sufficient control over the decompression, the algorithm converges to a novel solution that sets the current speed record in relation to the adiabatic timescale, beating out other experimental realizations based on theoretical approaches. This method presents a feasible approach for implementing fast state preparations or transformations in other quantum systems, without requiring a solution to a theoretical model of the system. Implications for fundamental physics and cooling are discussed. Significance Engineering the fast evolution of a quantum system between states is a key problem to be solved in the development of quantum technologies, such as quantum computing. We experimentally demonstrate a general approach using a Machine Learning algorithm that develops a model of the system, based on previous performance, to create further educated guesses on how to improve. Applied to a system similar to moving a cup of liquid between two locations (while blindfolded) the algorithm reaches a speed faster than previous approaches, dealing well with the complex dynamics and experimental imperfections present with its empirical approach. The resulting fast dynamics open the door to understanding how quantum mechanical systems reach equilibrium while the method provides a new tool to taming complex quantum systems.

Abstract:We have developed and characterised a stable, narrow linewidth external-cavity laser (ECL) tunable over 100 nm around 1080 nm, using a single-angled-facet gain chip. We propose the ECL as a low-cost, high-performance alternative to fibre and diode lasers in this wavelength range and demonstrate its capability through the spectroscopy of metastable helium. Within the coarse tuning range, the wavelength can be continuously tuned over 30 pm (7.8 GHz) without mode-hopping and modulated with bandwidths up to 3 kHz (piezo) and 37(3) kHz (current). The spectral linewidth of the free-running ECL was measured to be 22(2) kHz (Gaussian) and 4.2(3) kHz (Lorentzian) over 22.5 ms, while a long-term frequency stability better than 40(20) kHz over 11 hours was observed when locked to an atomic reference. 175-210 (2012). 18. List of parts and instruments. We used an Innolume GM-1060-150-PM-250 gain module, a Thorlabs C240TME-1064 mounted aspheric lens, a Thorlabs GR13-1210 blazed diffraction grating, a Thorlabs KMSS/M kinematic mirror mount, a Thorlabs PA4FKW piezo chip, European Thermodynamics APH-127-10-25-S TEC modules, an Epcos S861 thermistor, and an AFW Technologies PISO-83-2-C-7-2-FB polarization maintaining in-fibre isolator in the construction of the laser. The laser was controlled using a custom-built current controller, ILX Lightwave LDT-5100 temperature controllers, and a PiezoDrive PDu-150CL piezo driver. The laser was frequency stabilised using a Brimrose TEM-250-50-10-2FP fibre-coupled AOM, an SRS SR510 lock-in amplifier, and a custom-built PI controller.

We seem to talk about repeatable artworks, such as symphonies, plays, films, dances, and so on, all the time. We say things like, "The Moonlight Sonata has three movements" and "Duck Soup makes me laugh". But how are these sentences to be understood? On a simple treatment of these sentences, they have ordinary, subject-predicate form. The subject 2 refers to a repeatable artwork (e.g., The Moonlight Sonata, or Duck Soup) and the predicate ascribes some property to this artwork. The sentences are true just in case the individual referred to by the subject has the property ascribed to it by the predicate. Accepting this simple interpretation of the semantics of these sentences will have immediate consequences for our theory of repeatable artworks: the truth of the sentences will require that things like The Moonlight Sonata exist, that they are singular entities, and that they have the properties that the predicates in our sentences about them pick out. But perhaps the simple treatment of these sentences isn't the correct one. The surface form of a sentence isn't always a sure guide to its logical form. We are familiar with this phenomenon with respect to sentences like the following: 1. The average man has two and a half children. 2. Nothing is inside of the room. Neither of these sentences is such that the subject refers to some individual entity and the predicate tells us something about that entity. We will argue that the same is true of the following sentences: 3. The polar bear has four paws.

We present the detection of the highly forbidden 2 3 S 1 → 3 3 S 1 atomic transition in helium, the weakest transition observed in any neutral atom. Our measurements of the transition frequency, upper state lifetime, and transition strength agree well with published theoretical values and can lead to tests of both QED contributions and different QED frameworks. To measure such a weak transition, we develop two methods using ultracold metastable (2 3 S 1 ) helium atoms: low background direct detection of excited then decayed atoms for sensitive measurement of the transition frequency and lifetime, and a pulsed atom laser heating measurement for determining the transition strength. These methods could possibly be applied to other atoms, providing new tools in the search for ultraweak transitions and precision metrology.

The electrical activity of interfacial misfit dislocations in silicon has been examined using the electron beam induced current technique in a scanning electron microscope. Clean dislocations formed during high-temperature Si(Ge) chemical vapor epitaxy were studied. These defects were subsequently decorated with known metallic impurities (Au and Ni) by diffusion at different temperatures from a backside evaporated layer. Differences in electrical activity are discussed in relation to the detection limits of electron beam induced current technique and energy levels anticipated for the clean or decorated dislocations.

Ultracold collisions of Bose-Einstein condensates can be used to generate a large number of counterpropagating pairs of entangled atoms, which collectively form a thin spherical shell in momentum space, called a scattering halo. Here we generate a scattering halo initially composed of pairs in a symmetric entangled state in spin, and observe a coherent oscillation with an anti-symmetric state during their separation, due to the presence of an inhomogeneous magnetic field. We demonstrate a novel method of magnetic gradiometry based on the evolution of pairwise correlation, which is insensitive to common-mode fluctuations of the magnetic field. Furthermore, the highly multimode nature and narrow radial width of scattering halos enable a 3D reconstruction of the interrogated field. Based on this, we apply Ramsey interferometry to realise a 3D spatial reconstruction of the magnetic field without the need for a scanning probe.

Despite quantum electrodynamics (QED) being one of the most stringently tested theories underpinning modern physics, recent precision atomic spectroscopy measurements have uncovered several small discrepancies between experiment and theory. One particularly powerful experimental observable that tests QED independently of traditional energy level measurements is the “tune-out” frequency, where the dynamic polarizability vanishes and the atom does not interact with applied laser light. In this work, we measure the tune-out frequency for the 2 3 S 1 state of helium between transitions to the 2 3 P and 3 3 P manifolds and compare it with new theoretical QED calculations. The experimentally determined value of 725,736,700(260) megahertz differs from theory [725,736,252(9) megahertz] by 1.7 times the measurement uncertainty and resolves both the QED contributions and retardation corrections.

Elastic and inelastic proton scattering angular distributions of cross section and analyzing power were measured on three analog resonances at 10.30, 10.54, and 10.60 MeV in the ' Te-plus-proton system. The data have been analyzed using a coupled-channels-plus-resonance formalism. Opticalmodel parameters required for the analysis were obtained from measurements at two off-resonance energies. Polarization measurements carried out on two of these resonances are consistent with values predicted from the analysis of the cross-section and analyzing-power data. The analysis yields improved values of the spectroscopic amplitudes for coupling of nucleons to the ' Te 2+l core.