Clock atom interferometry is an emerging technique in precision measurement, well suited for sensitivity enhancement through large momentum transfer (LMT). Although next-generation sensors aim for LMT factors beyond $10^4$, their feasibility has been questioned due to potential impacts of laser frequency noise. We address this concern by analyzing the cumulative fidelity of sequential state inversions, showing that population error scales linearly with pulse number, not quadratically. Parasitic interferometer paths from imperfect pulses contribute negligibly, confirming that laser frequency noise is not a practical limitation.
Clock atom interferometry is an emerging technique in precision measurement, well suited for sensitivity enhancement through large momentum transfer (LMT). Although next-generation sensors aim for LMT factors beyond 104, their feasibility has been questioned due to potential impacts of laser frequency noise. We address this concern by analyzing the cumulative fidelity of sequential state inversions, showing that population error scales linearly with pulse number, not quadratically. Parasitic interferometer paths from imperfect pulses contribute negligibly, confirming that laser frequency noise is not a practical limitation.
Atom interferometry on optical clock transitions is being pursued for numerous long-baseline experiments both terrestrially and for future space missions. Crucial to meeting these experiments' required sensitivities is the implementation of large momentum transfer ($>10^3\hbar k$). Here we show that to sequentially apply such a large momentum via π pulses places stringent requirements on the frequency noise of the interferometry laser, finding that the linewidth is required to be considerably lower than has previously been suggested. This is due to imperfect pulse fidelity in the presence of noise and is apparent even for an atom at rest interacting with resonant light, making this a fundamental constraint on operational fidelity for a given laser and pulse sequence. Within this framework, we further present and analyse two high-power, frequency-stabilised laser sources designed to perform interferometry on the 1S0 - 3P0 clock transitions of cadmium and strontium, respectively operating at 332 nm and 698 nm.
Abstract Large momentum transfer (LMT) beam splitters are implemented in atom interferometers to increase their sensitivity. However, an LMT interferometer requires additional light pulses to modify the response function of the atom interferometer. In this paper, we develop an analytical model for the sensitivity function of LMT interferometers using sequential accelerating light pulses. We use the sensitivity function to calculate the acceleration sensitivity taking into account the pulse duration. In addition, the sensitivity to laser phase fluctuations is calculated, and we show that the pulse sequence can be engineered to mitigate the phase noise sensitivity.
Atom interferometric sensors can enable extremely precise measurements of inertial motion and external fields by manipulating and interfering atomic states using pulses of laser light. However, like many experiments that require the coherent control of a quantum system, the interaction fidelity is limited by inhomogeneities in the control fields. Variations in atomic velocity and laser intensity lead different atoms to experience different interactions under the same pulse, reducing the interference fringe contrast, introducing bias, and limiting the sensitivity. We present the theoretical design and experimental demonstration of pulses for atom interferometry which compensate inhomogeneities in atomic velocity and laser intensity. By varying the laser phase throughout a pulse and choosing an appropriate fidelity measure to be maximised, pulses are optimised by adapting optimal control techniques originally designed for nuclear magnetic resonance applications. We show using simulations that optimised pulses significantly improve the fidelity of interferometer operations and verify this experimentally using Raman transitions within a cold sample of 85Rb atoms. We demonstrate a robust state-transfer pulse that achieves a fidelity of 99.8(3)% in a ∼ 35 µK sample and obtain a threefold increase in the fringe contrast using a full sequence of optimised pulses. Many of the pulse shapes found by optimal control are simple and symmetrical, and we show that certain symmetries are integral to error compensation. By systematically exploring the dependence of these solutions on the model and optimisation parameters, we demonstrate a stability which underlines the general applicability of optimised pulses to a range of interferometer configurations. Finally, we introduce and computationally analyse a novel theoretical approach to improve the sensitivity of large-momentum-transfer (LMT) interferometers, whereby “biselective” pulses are optimised to track the changing resonance conditions encountered in extended pulse sequences that are designed to increase the measurement sensitivity. When conventional pulses of steady phase are used, the interference contrast decays rapidly as extra pulses are added because of the change in resonance. Using numerical simulations, we show that bi-selective pulses maintain interaction fidelity throughout extended pulse sequences, allowing significant increases in the sensitivity that may be obtained using LMT.
A point source interferometer (PSI) is a device where atoms are split and recombined by applying a temporal sequence of Raman pulses. During the pulse sequence, an initially trapped cloud of cold atoms is released and allowed to expand, behaving approximately as a point source. The PSI can work as a sensitive multi-axes gyroscope that can automatically filter out the signal from accelerations. The phase shift arising from rotations is proportional to the momentum transferred to each atom from the Raman pulses. Therefore, by increasing the momentum transfer, it should be possibly to enhance the sensitivity of the PSI. Here, we investigate the degree of enhancement in sensitivity that could be achieved by augmenting the PSI with large momentum transfer (LMT) employing a sequence of many Raman pulses with alternating directions. Contrary to typical approaches used for describing a PSI, we employ a model under which the motion of the center of mass of each atom is described quantum mechanically. We show how increasing Doppler shifts lead to imperfections, thereby limiting the visibility of the signal fringes, and identify ways to suppress this effect by increasing the effective, two-photon Rabi frequencies of the Raman pulses. Considering the effect of spontaneous emission, we show that for a given value of the one-photon Rabi frequency, there is an optimum value for the number of pulses employed, beyond which the net enhancement in sensitivity begins to decrease. For a one-photon Rabi frequency of 200 MHz, for example, the peak value of the factor of enhancement in sensitivity is ~39, for a momentum transfer that is ~69 times as large as that for a conventional PSI. We also find that this peak value scales as the one-photon Rabi frequency to the power of 4/5.
Large momentum transfer (LMT) enhances the gravitational phase of a light-pulse atom interferometer by a factor n, while mirrorless operation with momentum-resolved detection can quadruple the phase-carrying quantum Fisher information. These gains compete in practice because the momentum-space fringe period scales as 1/n, making the fringe signal increasingly vulnerable to finite detector resolution. We analyze this trade-off in a solvable model with instantaneous lossless n-photon pulses, a Gaussian source, and Gaussian detection blur, allowing continuous interpolation between Kasevich--Chu and mirrorless geometries. Closed-form expressions for the blurred output distributions and classical Fisher information are obtained, with a fringe-phase averaging approximation whose error is exponentially suppressed and agrees with numerical simulations at the 10−8 level. We find that mirrorless operation surpasses a conventional interferometer with the same momentum transfer only when σp<0.91m/(nk0T). Fringe-based readout exhibits an optimal momentum transfer n∗≃0.93m/(σpk0T) and a resolution-limited sensitivity floor Δg≃4.4σp/(mTN), independent of photon momentum. When this criterion is not satisfied, partial mirror asymmetry can recover part of the enhancement, whereas population-based readout remains insensitive to detector blur and ultimately favors the conventional sequence at sufficiently large n. Estimates for 87Rb sensors show that the mirrorless advantage is primarily restricted to short-baseline instruments.
Large-momentum-transfer (LMT) atom interferometers using elastic Bragg scattering on light waves are among the most precise quantum sensors to date. To advance their accuracy from the mrad to the μrad regime, it is necessary to understand the rich phenomenology of the Bragg interferometer, which differs significantly from that of a standard two-mode interferometer. We develop an analytic model for the interferometer signal and demonstrate its accuracy using comprehensive numerical simulations. Our analytic treatment allows the determination of the atomic projection noise limit of a LMT Bragg interferometer and provides the means to saturate this limit. It affords accurate knowledge of the systematic phase errors as well as their suppression by 2 orders of magnitude down to a few μrad using appropriate light-pulse parameters.