TY - JOUR AB - Frequency-stable lasers form the back bone of precision measurements in science and technology. Such lasers typically attain their stability through frequency locking to reference cavities. State-of-the-art locking performances to date had been achieved using frequency modulation based methods, complemented with active drift cancellation systems. We demonstrate an all passive, modulation-free laser-cavity locking technique (squash locking) that utilizes changes in spatial beam ellipticity for error signal generation, and a coherent polarization post-selection for noise resilience. By comparing two identically built proof-of-principle systems, we show a frequency locking instability of 5×10−7 relative to the cavity linewidth at 10 s averaging. The results surpass the demonstrated performances of methods engineered over the last five decades, potentially enabling an advancement in the precision control of lasers, while creating avenues for bridging the performance gaps between industrial grade lasers with scientific ones due to the afforded simplicity and scalability. AU - Diorico, Fritz R AU - Zhutov, Artem AU - Hosten, Onur ID - 14802 IS - 1 JF - Optica KW - Atomic and Molecular Physics KW - and Optics KW - Electronic KW - Optical and Magnetic Materials SN - 2334-2536 TI - Laser-cavity locking utilizing beam ellipticity: accessing the 10−7 instability scale relative to cavity linewidth VL - 11 ER - TY - JOUR AB - Precision sensing and manipulation of milligram-scale mechanical oscillators has attracted growing interest in the fields of table-top explorations of gravity and tests of quantum mechanics at macroscopic scales. Torsional oscillators present an opportunity in this regard due to their remarked isolation from environmental noise. For torsional motion, an effective employment of optical cavities to enhance optomechanical interactions—as already established for linear oscillators—so far faced certain challenges. Here, we propose a concept for sensing and manipulating torsional motion, where exclusively the torsional rotations of a pendulum are mapped onto the path length of a single two-mirror optical cavity. The concept inherently alleviates many limitations of previous approaches. A proof-of-principle experiment is conducted with a rigidly controlled pendulum to explore the sensing aspects of the concept and to identify practical limitations in a potential state-of-the art setup. Based on this study, we anticipate development of precision torque sensors utilizing torsional pendulums that can support sensitivities below 10−19Nm/√Hz, while the motion of the pendulums are dominated by quantum radiation pressure noise at sub-microwatts of incoming laser power. These developments will provide horizons for experiments at the interface of quantum mechanics and gravity. AU - Agafonova, Sofya AU - Mishra, Umang AU - Diorico, Fritz R AU - Hosten, Onur ID - 14980 IS - 1 JF - Physical Review Research TI - Zigzag optical cavity for sensing and controlling torsional motion VL - 6 ER - TY - JOUR AB - We study the impact of finite-range physics on the zero-range-model analysis of three-body recombination in ultracold atoms. We find that temperature dependence of the zero-range parameters can vary from one set of measurements to another as it may be driven by the distribution of error bars in the experiment, and not by the underlying three-body physics. To study finite-temperature effects in three-body recombination beyond the zero-range physics, we introduce and examine a finite-range model based upon a hyperspherical formalism. The systematic error discussed in this Letter may provide a significant contribution to the error bars of measured three-body parameters. AU - Agafonova, Sofya AU - Lemeshko, Mikhail AU - Volosniev, Artem ID - 13233 IS - 6 JF - Physical Review A SN - 2469-9926 TI - Finite-range bias in fitting three-body loss to the zero-range model VL - 107 ER - TY - JOUR AB - We build a parametric amplifier with a Josephson field-effect transistor (JoFET) as the active element. The resonant frequency of the device is field-effect tunable over a range of 2 GHz. The JoFET amplifier has 20 dB of gain, 4 MHz of instantaneous bandwidth, and a 1-dB compression point of -125.5 dBm when operated at a fixed resonance frequency. AU - Phan, Duc T AU - Falthansl-Scheinecker, Paul AU - Mishra, Umang AU - Strickland, W. M. AU - Langone, D. AU - Shabani, J. AU - Higginbotham, Andrew P ID - 13264 IS - 6 JF - Physical Review Applied TI - Gate-tunable superconductor-semiconductor parametric amplifier VL - 19 ER - TY - JOUR AB - We unveil a powerful method for the stabilization of laser injection locking based on sensing variations in the output beam ellipticity of an optically seeded laser. The effect arises due to an interference between the seeding beam and the injected laser output. We demonstrate the method for a commercial semiconductor laser without the need for any internal changes to the readily operational injection locked laser system that was used. The method can also be used to increase the mode-hop free tuning range of lasers, and has the potential to fill a void in the low-noise laser industry. AU - Mishra, Umang AU - Li, Vyacheslav AU - Wald, Sebastian AU - Agafonova, Sofya AU - Diorico, Fritz R AU - Hosten, Onur ID - 14749 IS - 15 JF - Optics Letters KW - Atomic and Molecular Physics KW - and Optics SN - 0146-9592 TI - Monitoring and active stabilization of laser injection locking using beam ellipticity VL - 48 ER - TY - JOUR AB - Proper operation of electro-optic I/Q modulators relies on precise adjustment and control of the relative phase biases between the modulator’s internal interferometer arms. We present an all-analog phase bias locking scheme where error signals are obtained from the beat between the optical carrier and optical tones generated by an auxiliary 2 MHz 𝑅𝐹 tone to lock the phases of all three involved interferometers for operation up to 10 GHz. With the developed method, we demonstrate an I/Q modulator in carrier-suppressed single-sideband mode, where the suppressed carrier and sideband are locked at optical power levels <−27dB relative to the transmitted sideband. We describe a simple analytical model for calculating the error signals and detail the implementation of the electronic circuitry for the implementation of the method. AU - Wald, Sebastian AU - Diorico, Fritz R AU - Hosten, Onur ID - 14759 IS - 1 JF - Applied Optics KW - Atomic and Molecular Physics KW - and Optics KW - Engineering (miscellaneous) KW - Electrical and Electronic Engineering SN - 1559-128X TI - Analog stabilization of an electro-optic I/Q modulator with an auxiliary modulation tone VL - 62 ER - TY - JOUR AB - Finding a feasible scheme for testing the quantum mechanical nature of the gravitational interaction has been attracting an increasing level of attention. Gravity mediated entanglement generation so far appears to be the key ingredient for a potential experiment. In a recent proposal [D. Carney et al., PRX Quantum 2, 030330 (2021)] combining an atom interferometer with a low-frequency mechanical oscillator, a coherence revival test is proposed for verifying this entanglement generation. With measurements performed only on the atoms, this protocol bypasses the need for correlation measurements. Here, we explore formulations of such a protocol, and specifically find that in the envisioned regime of operation with high thermal excitation, semiclassical models, where there is no concept of entanglement, also give the same experimental signatures. We elucidate in a fully quantum mechanical calculation that entanglement is not the source of the revivals in the relevant parameter regime. We argue that, in its current form, the suggested test is only relevant if the oscillator is nearly in a pure quantum state, and in this regime the effects are too small to be measurable. We further discuss potential open ends. The results highlight the importance and subtleties of explicitly considering how the quantum case differs from the classical expectations when testing for the quantum mechanical nature of a physical system. AU - Hosten, Onur ID - 10652 IS - 1 JF - Physical Review Research SN - 2643-1564 TI - Constraints on probing quantum coherence to infer gravitational entanglement VL - 4 ER - TY - JOUR AB - Lasers with well-controlled relative frequencies are indispensable for many applications in science and technology. We present a frequency-offset locking method for lasers based on beat-frequency discrimination utilizing hybrid electronic LC filters. The method is specifically designed for decoupling the tightness of the lock from the broadness of its capture range. The presented demonstration locks two free-running diode lasers at 780 nm with a 5.5-GHz offset. It displays an offset frequency instability below 55 Hz for time scales in excess of 1000 s and a minimum of 12 Hz at 10-s averaging. The performance is complemented with a 190-MHz lock-capture range, a tuning range of up to 1 GHz, and a frequency ramp agility of 200kHz/μs. AU - Li, Vyacheslav AU - Diorico, Fritz R AU - Hosten, Onur ID - 11438 IS - 5 JF - Physical Review Applied KW - General Physics and Astronomy SN - 2331-7019 TI - Laser frequency-offset locking at 10-Hz-level instability using hybrid electronic filters VL - 17 ER - TY - JOUR AB - Quantum entanglement has been generated and verified in cold-atom experiments and used to make atom-interferometric measurements below the shot-noise limit. However, current state-of-the-art cold-atom devices exploit separable (i.e., unentangled) atomic states. This perspective piece asks the question: can entanglement usefully improve cold-atom sensors, in the sense that it gives new sensing capabilities unachievable with current state-of-the-art devices? We briefly review the state-of-the-art in precision cold-atom sensing, focusing on clocks and inertial sensors, identifying the potential benefits entanglement could bring to these devices, and the challenges that need to be overcome to realize these benefits. We survey demonstrated methods of generating metrologically useful entanglement in cold-atom systems, note their relative strengths and weaknesses, and assess their prospects for near-to-medium term quantum-enhanced cold-atom sensing. AU - Szigeti, Stuart S. AU - Hosten, Onur AU - Haine, Simon A. ID - 9331 IS - 14 JF - Applied Physics Letters SN - 00036951 TI - Improving cold-atom sensors with quantum entanglement: Prospects and challenges VL - 118 ER - TY - JOUR AB - We demonstrate the utility of optical cavity generated spin-squeezed states in free space atomic fountain clocks in ensembles of 390 000 87Rb atoms. Fluorescence imaging, correlated to an initial quantum nondemolition measurement, is used for population spectroscopy after the atoms are released from a confining lattice. For a free fall time of 4 milliseconds, we resolve a single-shot phase sensitivity of 814(61) microradians, which is 5.8(0.6) decibels (dB) below the quantum projection limit. We observe that this squeezing is preserved as the cloud expands to a roughly 200  μm radius and falls roughly 300  μm in free space. Ramsey spectroscopy with 240 000 atoms at a 3.6 ms Ramsey time results in a single-shot fractional frequency stability of 8.4(0.2)×10−12, 3.8(0.2) dB below the quantum projection limit. The sensitivity and stability are limited by the technical noise in the fluorescence detection protocol and the microwave system, respectively. AU - Malia, Benjamin K. AU - Martínez-Rincón, Julián AU - Wu, Yunfan AU - Hosten, Onur AU - Kasevich, Mark A. ID - 8285 IS - 4 JF - Physical Review Letters SN - 0031-9007 TI - Free space Ramsey spectroscopy in rubidium with noise below the quantum projection limit VL - 125 ER - TY - JOUR AB - We demonstrate that releasing atoms into free space from an optical lattice does not deteriorate cavity-generated spin squeezing for metrological purposes. In this work, an ensemble of 500000 spin-squeezed atoms in a high-finesse optical cavity with near-uniform atom-cavity coupling is prepared, released into free space, recaptured in the cavity, and probed. Up to ∼10 dB of metrologically relevant squeezing is retrieved for 700μs free-fall times, and decaying levels of squeezing are realized for up to 3 ms free-fall times. The degradation of squeezing results from loss of atom-cavity coupling homogeneity between the initial squeezed state generation and final collective state readout. A theoretical model is developed to quantify this degradation and this model is experimentally validated. AU - Wu, Yunfan AU - Krishnakumar, Rajiv AU - Martínez-Rincón, Julián AU - Malia, Benjamin K. AU - Hosten, Onur AU - Kasevich, Mark A. ID - 8319 IS - 1 JF - Physical Review A SN - 24699926 TI - Retrieval of cavity-generated atomic spin squeezing after free-space release VL - 102 ER -