The precise measurement of the energy states of individual atoms has long been a challenge for physicists. This difficulty stems from atomic recoil, a phenomenon that occurs when an atom interacts with a photon and recoils in the opposite direction. This recoil makes it challenging to accurately determine the position and momentum of the atom. The implications of atomic recoil are significant, particularly in the field of quantum sensing, where detecting minute changes in parameters is essential. For example, changes in gravitational waves can provide insights into the shape of the Earth or help detect dark matter.
In a groundbreaking paper published in Science, researchers at JILA and NIST introduced a novel approach to overcoming atomic recoil. The team, led by JILA Fellows Ana Maria Rey, James Thompson, and Murray Holland, proposed a new type of atomic interaction known as momentum-exchange interaction. This interaction involves atoms exchanging their momentums by exchanging corresponding photons. By conducting experiments within a cavity, an enclosed space composed of mirrors, the researchers observed that atomic recoil could be dampened by allowing atoms to exchange energy states within the confined space. This process led to a collective absorption of energy and distributed the recoil across the entire population of particles.
The results of this study have significant implications for quantum physics research. Researchers can now design cavities to mitigate the effects of recoil and other external influences in a wide range of experiments, allowing for a better understanding of complex systems and the discovery of new aspects of quantum physics. Furthermore, an improved cavity design could enable more precise simulations of phenomena such as the Bose-Einstein-Condensate-Bardeen-Cooper-Schrift (BEC-BCS) crossover or high-energy physical systems.
For the first time, researchers observed that the momentum-exchange interaction induced one-axis twisting (OAT) dynamics, a critical aspect of quantum entanglement, between atomic momentum states. OAT acts as a quantum braid, entangling different molecules by twisting and connecting each quantum state to another particle. Previously, OAT was only observed in atomic internal states, but with this new discovery, it is believed that OAT induced by momentum exchange could help reduce quantum noise from multiple atoms. The ability to entangle momentum states could lead to improvements in physical measurements by quantum sensors, particularly in the detection of gravitational waves.
A key aspect of the researchers’ approach involved forcing atoms to exchange photons and their associated energy to control atomic recoil effectively. This process can be likened to a game of dodgeball, where atoms exchange photons, resulting in opposite recoils that cancel each other out. By exchanging different photon energies, atoms can create a momentum graph known as a density grating, resembling a fine-toothed comb. This formation indicates coherence between two momentum states within an atom, allowing them to interfere with each other.
The researchers also discovered that their control method could help address the issue of the Doppler shift in atomic measurements. The Doppler shift is a phenomenon that describes changes in frequency or energy due to relative motion. In the realm of quantum physics, the Doppler shift can pose challenges for achieving precise measurements. By simulating their new approach, the researchers found that it could mitigate measurement distortions caused by the Doppler shift, enhancing the accuracy of spectroscopic analyses.
Furthermore, the momentum exchange between atoms was found to exhibit characteristics of quantum entanglement. Researchers observed that as an atom’s motion influenced the cavity frequency, other atoms collectively responded to this feedback mechanism, correlating their motions. By inducing a significant separation between the momentum states of atoms and then initiating momentum exchange, the researchers demonstrated a persistent connection between the atoms, akin to being linked by a spring.
Looking ahead, the researchers plan to delve deeper into this newfound form of quantum entanglement. By understanding how it can be leveraged to enhance various types of quantum devices, the researchers aim to unlock new possibilities for advancing measurement techniques and studying complex quantum phenomena.