Long-baseline precision tests based on atom interferometry require drastic control over the initial external degrees of freedom of atomic ensembles to reduce systematic effects. The use of optical lattices (OLs) is a highly accurate method to manipulate atomic states in position and momentum allowing excellent control of the launch in atomic fountains. The simultaneous lattice launch of two atomic species, as required in a quantum test of the equivalence principle, is however problematic due to crosstalk effects. In this article, we propose to selectively address two species of alkalines by applying two OLs at or close to magic-zero wavelengths of the atoms. The proposed scheme applies in general for a pair of species with a vastly different ac Stark shift to a laser wavelength. We illustrate the principle by studying a fountain launch of condensed ensembles of 87 Rb and 41 K initially co-located. Numerical simulations confirm the fidelity of our scheme up to few nm and nm s −1 in inter-species differential position and velocity, respectively. This result is a pre-requisite for the next performance level in precision tests.
Long-baseline precision tests based on atom interferometry require drastic control over the initial external degrees of freedom of atomic ensembles to reduce systematic effects. The use of optical lattices (OLs) is a highly accurate method to manipulate atomic states in position and momentum allowing excellent control of the launch in atomic fountains. The simultaneous lattice launch of two atomic species, as required in a quantum test of the equivalence principle, is however problematic due to crosstalk effects. In this article, we propose to selectively address two species of alkalines by applying two OLs at or close to magic-zero wavelengths of the atoms. The proposed scheme applies in general for a pair of species with a vastly different ac Stark shift to a laser wavelength. We illustrate the principle by studying a fountain launch of condensed ensembles of 87 Rb and 41 K initially co-located. Numerical simulations confirm the fidelity of our scheme up to few nm and nm s −1 in inter-species differential position and velocity, respectively. This result is a pre-requisite for the next performance level in precision tests.
Atom interferometry tests of universality of free fall based on the differential measurement of two different atomic species provide a useful complement to those based on macroscopic masses. However, when striving for the highest possible sensitivities, gravity gradients pose a serious challenge. Indeed, the relative initial position and velocity for the two species need to be controlled with extremely high accuracy, which can be rather demanding in practice and whose verification may require rather long integration times. Furthermore, in highly sensitive configurations gravity gradients lead to a drastic loss of contrast. These difficulties can be mitigated by employing wave packets with narrower position and momentum widths, but this is ultimately limited by Heisenberg's uncertainty principle. We present a promising scheme that overcomes these problems by compensating the effects of the gravity gradients and circumvents the fundamental limitations due to Heisenberg's uncertainty principle. Furthermore, it relaxes the experimental requirements on initial colocation by several orders of magnitude.
We discussed possible improvement methods for a dual-species atom interferometry test of the weak equivalence principle (WEP) at the 10^(-12) level. The original research tested the WEP by comparing the acceleration difference of the free-fallen rubidium isotopes atom clouds. Based on the percent uncertainty presented from this test, AC stark shift is the most significant obstacle to improving precision. This article will discuss a precision-improving method to the original test by suppressing the background AC stark shift by centering the interferometry lasers to their "magic frequency." The expected improved precision of the uncertainty level is below the 10^(-18) level. Due to the limitation of instruments, we have yet to test this improving method in the actual measurement. Still, we analyzed the possible difficulties in practical usage and discussed solving strategies that correspond to the problems.
Optical lattice clocks combine the accuracy and stability required for next-generation frequency standards. At the heart of these clocks are carefully engineered optical lattices tuned to a wavelength where the differential AC Stark shift between ground and excited states vanishes—the so called ‘magic’ wavelength. To date, only alkaline-earth-like atoms utilizing clock transitions with total electronic angular momentum J=0 have successfully realized these magic wavelength optical lattices at the level necessary for state-of-the-art clock operation. In this article, we discuss two additional types of clock transitions utilizing states with J≠0, leveraging hyperfine structure to satisfy the necessary requirements for controlling lattice-induced light shifts. We propose realizing (i) clock transitions between same-parity clock states with total angular momentum F=0 and (ii) M1/E2 clock transitions between a state with F=0 and a second state with J=1/2, mF=0. We present atomic species which fulfill these requirements before giving a detailed discussion of both manganese and copper, demonstrating how these transitions provide the necessary suppression of fine structure-induced vector and tensor lattice light shifts for clock operations. Such realization of alternative optical lattice clocks promises to provide a rich variety of new atomic species for neutral atom clock operation, with applications from many-body physics to searches for new physics.
We report on the progress toward a dual-species cadmium and strontium atom interferometer for fundamental physics tests. We have developed and characterized a complete baseline laser system for cadmium, which provides the high power and narrow linewidth necessary for laser cooling and trapping and for performing atom interferometry, with upgraded systems for strontium also implemented. An overview of a design for cooling cadmium is presented, and we outline the basic design of a Cd–Sr atomic fountain, discussing atom launching techniques and the possible role of blackbody radiation. The excellent properties of cadmium and strontium, both individually and as a test pair, are discussed along with the enabled fundamental physics program of tests of the weak equivalence principle and the measurement of relativistic time dilation effects in quantum superpositions of clocks.
The utilization of light-pulse atom interferometry presents a valuable technique that has found application in both fundamental scientific inquiries, such as investigating constants such as measurements of fine structure constant α and gravitational constant G, and practical endeavors including acceleration sensing and rotation measurements. This thesis delves into our implementation of a dual atom interferometer design involving the clock transition 1S0 → 3P0 in strontium, concurrently conducting the interferometric sequence on atoms in both ground and excited states. To facilitate the dual atom interferometer’s operation, we have firstly established a compact experimental setup with a transversely loaded bi-dimensional magneto-optical-trap (2D-MOT) to create a high flux source of cold strontium atoms. Introducing a novel cross-polarized bi-color atomic beam slower, we simultaneously addresses two excited Zeeman substates of the transition 1S0 → 1P1 in strontium-88, significantly enhancing the number of atoms prepared in the 461 nm MOT by around 10-fold. Following the 461 nm MOT, the atomic ensemble undergoes cooling in a 689 nm MOT, achieving atomic temperatures below 1 µK. We also install a network of eight magnetic field probes arranged around the cold atomic sample, enabling precise three-axis active control of magnetic fields down to the milligauss level. With the atoms confined in a 2D lattice at the magic-wavelength of 813.427 nm after the initial preparation phase, we conduct the magnetically-induced clock transition to create a statistical mixture state of ground and excited states. After a velocity selection stage, implementing a Mach-Zehnder interferometer with Bragg pulses operating at the magic-wavelength along the vertical axis, we conduct tests of the weak equivalence principle (WEP). The Eötvös ratio we found in our system stood at (1.8 ± 3.1) × 10−4, mainly limited by the finite temperature of the atomic cloud constraining the interrogation time. Furthermore, the dual atom interferometer scheme enables the measurement of state-dependent force and eventually polarizability difference via the phase shift between the atoms in different states, and we experimentally demonstrate this by introducing an additional light field gradient.
We demonstrate the cancellation of the differential ac Stark shift of the microwave hyperfine clock transition in trapped 87 Rb atoms. Recent progress in metrology exploits so-called “magic wavelengths,” whereby an atomic ensemble can be trapped with laser light whose wavelength is chosen so that both levels of an optical atomic transition experience identical ac Stark shifts. Similar magic-wavelength techniques are not possible for the microwave hyperfine transitions in the alkalis, due to their simple electronic structure. We show, however, that ac Stark shift cancellation is indeed achievable for certain values of wavelength, polarization, and magnetic field. The cancellation comes at the expense of a small magnetic-field sensitivity. The technique demonstrated here has implications for experiments involving the precise control of optically-trapped neutral atoms.