Atom Interferometric Quantum Sensors Define Inertial Phase Using Single Temporal Pulse Origin

Atom interferometers represent a powerful new approach to precision sensing, offering the potential to measure inertial and gravitational effects with unprecedented accuracy, but practical limitations often compromise their stability. Jack Saywell, Nikolaos Dedes, and Max Carey, all from the University of Southampton, alongside Brynle Barrett from the University of New Brunswick and Tim Freegarde from the University of Southampton, now demonstrate a crucial insight into how these sensors respond to the control pulses that manipulate atoms. Their work reveals that the inertial response of each pulse can be accurately described by a single point in time, termed the ‘temporal origin’, which simplifies the determination of the sensor’s scale factor and makes it less susceptible to environmental noise. This discovery not only explains previously observed systematic errors in existing devices, but also provides a pathway to designing shorter, more robust pulses, promising significant improvements in the performance of both current and future atom interferometric sensors.

Atom Interferometry, Pulse Timing and Systematic Errors

Quantum sensors based on atom interferometry utilise radio-frequency or optical pulses to manipulate atomic wavepackets for sensing, creating the superposition needed for interferometric measurement. This work investigates how uncertainty in pulse timing impacts atom interferometric measurements and develops methods to mitigate these effects. The research team employs a novel approach to characterise and correct for pulse timing errors, utilising a precision timing system and advanced data analysis techniques. They demonstrate that even small uncertainties in pulse timing can significantly degrade the accuracy of atom interferometric measurements, particularly for sensors operating at low frequencies.

This calibration substantially reduces systematic errors, improving the overall performance of the atom interferometer. Furthermore, the study explores shaped pulses to enhance sensor sensitivity and robustness, improving the signal-to-noise ratio and allowing for more accurate measurements of weak signals. The results demonstrate the potential for highly sensitive and precise quantum sensors based on atom interferometry, with applications in gravitational wave detection, inertial sensing, and fundamental physics research.

Temporal Origin Defines Atom Interferometry Pulses

This research demonstrates a new understanding of how to characterise and optimise pulses used in atom interferometry, a technology used for highly precise measurements of inertial and gravitational effects. Scientists have shown that the inertial response of any pulse can be defined by a single point in time, termed the ‘temporal origin’, which allows for a simplified and accurate determination of the sensor’s measurement scale factor. Crucially, establishing a stable temporal origin significantly improves the stability of this scale factor and minimises errors caused by fluctuations in experimental conditions. The team’s simulations reveal that incorporating the temporal origin as a design parameter enables the creation of shorter, more robust pulses, enhancing the performance of current and future interferometric sensors. By relaxing conventional constraints on pulse design, they achieved improved fidelity with reduced pulse area, which is particularly beneficial for experiments utilising two-photon Raman transitions where minimising spontaneous emission is critical.

Optimized Pulse Sequences Enhance Atom Interferometry Sensitivity

Atom interferometry is a highly sensitive technique for measuring acceleration, gravity, rotation, and other inertial effects, relying on splitting, manipulating, and recombining the wave functions of atoms. Precisely timed sequences of laser pulses control the atoms’ momentum and internal states within the interferometer, and optimisation involves finding the best pulse shapes and timings to maximise sensitivity and minimise errors. Accurately determining the scale factor, a measure of the interferometer’s sensitivity, is crucial for precise measurements. Robust control designs pulse sequences less sensitive to imperfections in the experimental setup, such as laser frequency fluctuations and atom temperature.

Optimal control theory finds the best control signals to achieve a desired outcome, maximising the sensitivity of the interferometer by carefully shaping the laser pulses to create specific atomic momentum distributions and phase evolutions. Pulse shape optimisation techniques include gradient ascent, broadband pulse usage, and precise phase dispersion control, achieving robustness through broadband excitation and optimised rotation pulses. Numerical simulations, using software tools like Spinach and QuTiP, model the behaviour of the atoms and optimise the pulse sequences. Careful consideration of experimental imperfections is essential for achieving high-precision measurements.

Temporal Origin Defines Atom Interferometry Scale Factor

Atom interferometers manipulate atomic states to make precise measurements of inertial and gravitational effects. A key advantage of these sensors is often considered to be their precisely known and stable measurement scale factor. However, the finite duration of the pulses used in these sensors makes the scale factor dependent on pulse shape and sensitive to variations in control field intensity, frequency, and atomic velocity. This research explores the concept of a temporal pulse origin in atom interferometry, where the inertial phase response of any pulse can be parameterised using a single point in time.

The team shows that the temporal origin allows for a simple determination of the measurement scale factor, independent of pulse shape, control field parameters, and atomic velocity distributions. This approach effectively decouples the scale factor from these sensitivities, enhancing the precision and reliability of atom interferometry measurements. The method involves characterising the temporal evolution of the atomic wavepacket during each pulse interaction, allowing for a precise definition of the effective pulse area and phase, simplifying data analysis and reducing systematic errors.