High-Fidelity Superpositions Advance Bose-Einstein Condensate Quantum Computation Techniques

Scientists are increasingly focused on the precise control of ultracold atoms to advance technologies including quantum computation. Renzo Testa and Donatella Cassettari, both from the SUPA School of Physics & Astronomy at the University of St Andrews, alongside colleagues, detail a novel and efficient method for manipulating Bose-Einstein condensates using time-dependent optical fields. Their research demonstrates the numerical engineering of superpositions of persistent currents within a toroidal trap with high fidelity, and importantly, provides an analytical model predicting the stability of these states over time, representing a significant step towards robust quantum systems.

This work details the numerical engineering of superpositions of persistent currents within a toroidal trap, attaining remarkably high fidelity. The study also meticulously examines the long-term stability of these states, presenting an analytical two-state model that accurately predicts their evolution even in the presence of self-interactions.

The team achieved a breakthrough in controlling the Wave function of ultracold atoms by independently manipulating both its amplitude and phase. This innovative approach allows for the creation of arbitrary motional states within the Bose-Einstein condensate, offering unprecedented flexibility in quantum control. Specifically, the researchers focused on generating superpositions of persistent currents in toroidal traps, a configuration crucial for developing advanced atomtronic devices. By shaping the trapping potential with time-dependent optical fields and simultaneously imprinting a phase, they effectively ‘program’ the condensate’s wave function to achieve the desired superposition state.

Experiments show that this technique relies on a combination of dynamically altering the trapping potential and applying a precisely timed phase imprint to the condensate’s wave function. The researchers illustrate this principle using a simplified example with a linear trap, demonstrating how a ground state condensate can be transformed into an excited state through the removal of barriers and the application of a π-phase imprint to specific lobes of the wave function. This process, validated through numerical simulations, minimizes discrepancies between the engineered state and the target state, even accounting for the limitations of real-world barrier heights and widths. The research establishes a pathway towards creating superpositions of persistent currents in two-dimensional ring geometries, a critical step for realising compact and portable atom interferometers.

Starting with a single persistent current state, the team defines a target state as a superposition, represented mathematically as a combination of opposing angular momentum states. This superposition results in a unique atomic density distribution, described by a cosine function, paving the way for sensitive measurements of rotations and magnetic fields. The work opens possibilities for quantum information processing and advanced quantum sensing applications, leveraging the long-lived nature of persistent currents in ring traps.

Bose-Einstein condensate control via shaped light fields offers

Scientists engineered a novel method for manipulating the motional state of Bose-Einstein condensates using time-dependent optical fields, offering precise control for applications in quantum sensing and computation. The research team developed a technique to create superpositions of persistent currents within a toroidal trap, achieving high fidelity through careful manipulation of the condensate’s wave function. This work hinges on independent control of both the amplitude and phase of the condensate, accomplished by shaping the trapping potential and imprinting a phase via pulsed optical fields. Specifically, the study harnessed fast-scanning acousto-optic deflectors, digital micromirror devices, and liquid-crystal spatial light modulators to achieve spatio-temporal control of light intensity.

Researchers employed numerical simulations to demonstrate the feasibility of engineering these superpositions, meticulously modelling the condensate’s behaviour within the toroidal trap. The computational work involved defining the trapping potential and applying time-dependent optical fields to induce the desired motional states. Experiments utilized a linear trap as a starting point, investigating control of vibrational states through gradual trap deformation and time-dependent perturbations. Simulations transferred the condensate from a ground state to an excited state by gradually modifying the trap geometry, mirroring approaches found in previous studies.

The study pioneered a wave function engineering protocol, initially considered within the simplified context of a linear trap with no self-interactions, to establish the fundamental principles. This protocol relies on shaping the trapping potential to control amplitude and applying a phase imprint using pulsed optical fields, a technique previously used to generate dark solitons and vortices. To assess the fidelity and stability of the engineered states, the team conducted detailed numerical analyses, focusing on the evolution of the superposition over time. An analytical two-state model was also developed to approximate the condensate’s behaviour, particularly in the presence of self-interactions, providing a simplified framework for understanding the observed dynamics.

This approach enables the creation of guided atom interferometers with uniformly spread interfering waves around the ring, potentially enhancing sensitivity in rotation or magnetic field measurements. The team’s method achieves a level of control previously unattainable, paving the way for advanced atomtronic devices and quantum information processing applications. The research demonstrates a significant advancement in manipulating ultracold atoms, offering a versatile platform for exploring fundamental quantum phenomena and developing innovative technologies.

Persistent Current Superpositions in Toroidal BECs reveal novel

Scientists have developed a novel and efficient method for manipulating the motional state of Bose-Einstein condensates using time-dependent optical fields. This technique enables the engineering of superpositions of persistent currents within a toroidal trap, demonstrating high fidelity in numerical simulations. The research details a process for precisely controlling the quantum state of ultracold atoms, a crucial step for advancements in quantum computation and sensing. The study successfully demonstrates the creation of stable superpositions, even when accounting for the effects of self-interactions between atoms.

An analytical two-state model accurately predicts the evolution of these states over time, confirming their robustness. Furthermore, the protocol is broadly applicable, allowing for the engineering of arbitrary wave functions and potentially extending to imbalanced superpositions of persistent currents or excited states within linear traps. Acknowledging certain limitations, the authors note that the fidelity of the engineered states can be affected by barrier height and the degree of atomic interactions. Future research will focus on exploring the application of this control method for quantum information schemes, specifically encoding information in external degrees of freedom. This work represents a significant step towards harnessing the potential of Bose-Einstein condensates for advanced quantum technologies and precision measurement, including rotation sensing.