Redefining what Information is Vital in Quantum Measurements
Scientists at the Korea Institute of Science and Technology (KIST) have attempted to capture the interaction between different kinds of information that are essential while gathering quantum measurements, specifically information gain, disturbance, and reversibility. Their paper, released in Physical Review Letters, represents these three key quantities associated with quantum measurement in a single compromise relation for the first time.
Seung-Woo Lee and Hyang-Tag Lim at the KIST Center for Quantum Information told Phys.org that the principle of compromise between information gain and the disturbance was understood before (i.e., if the intention is to acquire information regarding a quantum state or system, we inevitably disrupt the state or the system, and it changes to some other state while doing so). They continued by adding that the concept of reversibility was additionally explored previously, however, not along with information gain and disturbance.
Information gain, disturbance, and reversibility are three essential quantities influencing quantum measurement procedures. The primary purpose of the work by Lee, Lim, and their coworkers was to show that there is a compromise relation between all these three amounts.
To accomplish this, the team developed an interferometer, an optical tool that combines two or more light sources to produce an interference pattern that can then be measured and assessed. The interferometer they created has three optical pathways and can combine photonic qutrits (units of quantum information) with path degrees of freedom.
Lim clarified that in quantum optics, one could generate and adjust a photonic qudit state using different single photon’s degrees of freedom like optical path, polarization, time-bin, orbital angular momentum, etc.
Lim added that by using the interferometer, the team collected different quantum measurements by adjusting the transmission amplitude for every path. The transmission amplitude for every path was regulated using direct optical devices, such as polarizing beam splitters and half waveplates.
Lim and his coworkers, based on the measurements they collected, were then able to approximate three kinds of information and demonstrate a full information trade-off by controlling a photonic qutrit state and the strengths of quantum measurement. Their findings reveal that quantum measurements divided the information of a quantum state into three different aspects, specifically the disturbance, information gain, and reversibility.
Lee claimed that his team’s primary contribution brought these three concepts under one roof for the first time, revealing a single trade-off relation containing all three elements. Lee and his team revealed that the three amounts are interlinked and based on each other. The research redefines what quantities are essential for a quantum measurement and their values for a measurement in a quantum information task to be ideal.
The findings collected by this group of scientists may have countless essential implications, as they define the most crucial quantities for maintaining information while taking quantum measurements. In addition to motivating new quantum research, this work may even lead to the development of safer quantum data processing devices.
Lee included that now there can be numerous new research paths to pursue. Lee added that the first is to examine identical trade-off relations in multi-particle systems in the presence or lack of entanglement and other types of correlations.
An additional is to capture the concept of information loss in the framework of trade-off relation, including the three quantities, in the presence and absence of interference. Ultimately, the team will attempt to connect this framework to the models of decoherence and examine how information loss scales with decoherence when examined in the context of this compromise relation.
Originally published by: phys.org
