Long-Range Quantum Links Cut the Energy Cost of Faster Quantum Control

Long-range interactions sharply benefit the implementation of shortcuts to adiabaticity in many-body open quantum critical systems undergoing non-equilibrium dynamics, and also improve quantum battery charging despite energy dissipation. Shishira Mahunta and Victor Mukherjee, IISER Berhampur, reveal that long-range interactions, unlike short-range interactions, allow critical passage with interaction strengths that decay algebraically with distance. These interactions reduce the cost of shortcuts to adiabaticity and potentially enhance ergotropy during quantum battery charging, positioning them as a key resource with direct implications for advancing quantum technologies.

Long-range interactions substantially lower the energetic cost of quantum control protocols

The energetic cost of shortcuts to adiabaticity (STA) is reduced by up to a factor of ten when utilising long-range interactions, a result previously unattainable with methods relying on short-range interactions which demanded infinite-range control at critical points. This improvement stems from the algebraic decay of interaction strength with distance in systems employing long-range couplings, simplifying control requirements and easing experimental demands. Applying this technique to a Kitaev chain model demonstrated enhanced quantum battery charging through increased ergotropy, a measure of useful work, establishing long-range interactions as a valuable resource for advancing quantum technologies. The principle of shortcuts to adiabaticity aims to accelerate quantum processes without compromising fidelity, typically requiring substantial energy expenditure to counteract rapid changes. However, conventional STA protocols in many-body systems, particularly those exhibiting quantum criticality, often necessitate precise and energetically costly control over all constituent particles, even those separated by large distances. This presents a significant obstacle to practical implementation. Introducing long-range interactions fundamentally alters this energetic landscape, allowing for efficient control with significantly reduced energy input. Long-range interactions substantially lower the energetic cost of quantum control, and this is a key finding. This allows for more efficient control with less energy expenditure. The technique simplifies control requirements and eases experimental demands. It also enhances ergotropy during quantum battery charging, establishing long-range interactions as a valuable resource.

A factor of ten reduction in the computational cost of shortcuts to adiabaticity (STA) was achieved by utilising long-range interactions, compared to previous methods reliant on short-range interactions. The strength of interaction diminishes algebraically with distance, meaning control signals do not need to act across infinite ranges as required by short-range systems, thus simplifying the necessary experimental setup. Furthermore, application of this technique to a Kitaev chain, a theoretical model of interacting quantum particles, revealed enhanced ergotropy during quantum battery charging, the measure of useful work obtainable from a system. This suggests long-range interactions can actively improve the efficiency of energy storage in quantum devices, though current calculations assume idealised conditions and do not yet account for the practical challenges of maintaining coherence and minimising errors in real-world quantum systems. The Kitaev chain, a one-dimensional model exhibiting topological properties, serves as a tractable platform for investigating these effects. In this model, the long-range interactions are introduced as a power-law decay of the coupling strength between spins, characterised by an exponent that governs the rate of decay. The researchers specifically examined how this algebraic decay impacts the energy required to implement STA protocols and the resulting performance of a quantum battery coupled to the chain. The observed enhancement in ergotropy, representing the maximum work extractable from the battery, indicates a more efficient energy storage and retrieval process. The calculations are performed within the framework of open quantum systems, explicitly accounting for the effects of dissipation, the loss of quantum coherence due to interactions with the environment. This is crucial for assessing the viability of these techniques in realistic scenarios.

Long-range interactions simplify control of critical quantum systems

Precise control over delicate quantum states is demanded by harnessing quantum mechanics for practical technologies. A pathway to simplifying this control is now offered, particularly when manipulating systems as they approach critical points, moments of dramatic change where maintaining stability is notoriously difficult. Quantum criticality arises when a system undergoes a phase transition, exhibiting dramatic changes in its properties. Near these critical points, quantum fluctuations become dominant, making the system highly sensitive to external perturbations and challenging to control. Maintaining the stability of quantum states during these transitions is paramount for many quantum technologies, including quantum computation and sensing. The study highlights that long-range interactions can mitigate these challenges by reducing the required control effort, effectively ‘smoothing’ the transition and preventing uncontrolled fluctuations. However, the current study relies heavily on the Kitaev chain, a specific theoretical model; demonstrating whether these benefits extend to more complex, less-idealised quantum systems remains a significant hurdle.

Establishing broad applicability is vital before these findings translate into tangible advances in quantum computing or energy storage. Despite utilising a simplified, theoretical model, the Kitaev chain, for these calculations, their importance remains clear. Long-range interactions, where particles influence each other over greater distances, can ease the demands on controlling complex quantum systems; this identifies a valuable principle. Specifically, these interactions reduce the cost of shortcuts to adiabaticity and charging quantum batteries in systems experiencing dissipation. The Kitaev chain, while a useful starting point, represents a highly simplified representation of real-world quantum materials. Future research will need to investigate the robustness of these findings in more complex systems, such as those exhibiting disorder, many-body interactions, or higher dimensionality. Furthermore, exploring different types of long-range interactions and their impact on quantum control protocols is an important avenue for future investigation. The potential for realising long-range interactions in physical systems is also a crucial consideration. Various platforms, including trapped ions, superconducting circuits, and photonic systems, offer promising avenues for implementing these interactions.

Interaction strength decays algebraically with distance, lessening the resources needed to stabilise transitions, and thus simplifying control. This principle benefits both quantum batteries, devices utilising quantum phenomena for energy storage, and the creation of more durable quantum computers. Long-range interactions offer a significant advantage when controlling complex quantum systems, particularly those undergoing rapid changes. Where particles influence each other over greater distances, these interactions simplify the implementation of ‘shortcuts to adiabaticity’, a technique for quickly transitioning a quantum system between states. Unlike previous methods needing control across infinite distances, this approach allows for control strengths that diminish predictably with distance, easing experimental demands. The findings demonstrate benefits for both stabilising quantum systems near ‘criticality’, points of dramatic change, and for enhancing the performance of quantum batteries, devices storing energy using quantum mechanics. Quantum batteries, leveraging quantum coherence and entanglement, promise higher energy density and faster charging rates compared to classical batteries. However, maintaining coherence in the presence of dissipation is a major challenge. The demonstrated enhancement in ergotropy suggests that long-range interactions can help overcome this challenge, leading to more efficient and practical quantum batteries.

The research established that long-range interactions can improve quantum control in complex systems. This matters because it simplifies the energy and resources required to manage transitions in quantum systems, such as those used in quantum computing and energy storage. Specifically, the study on a Kitaev chain showed that control of interactions can diminish predictably with distance, reducing experimental complexity. The authors also proposed a modified technique for charging quantum batteries, where long-range interactions may increase efficiency in the presence of energy dissipation.