Quantum Resource Theories: From Entanglement to Time Correlations and Measurement-Induced Noise

Dear Colleagues,

Initially, quantum technology schemes were routinely designed around the use of entanglement as their main resource. For example, quantum cryptography often uses highly entangled photon pairs to establish cryptographic keys between users. Moreover, quantum metrology often uses highly entangled photon states for beating the standard quantum limit in interferometric phase measurements. In addition, entangling quantum gates are an essential building block for quantum computing. However, entanglement is not always easy to generate and in recent years, attention has shifted to include alternative quantum resources. The question, where is the border between quantum and classical physics, lies at the center of many ongoing research projects that aim at obtaining a more accurate picture of available quantum resources.

Generally, quantum information is processed using unitary dynamics and subsequent measurements. Recently, it has been shown that generalized measurements can produce non-classical time correlations even in the absence of entanglement. This realization has led, for example, to the development of hidden quantum Markov models with applications in quantum metrology. In addition to generalized measurements, there are numerous other quantum resources that are currently being explored. These include causality violations and entanglement in time with applications such as quantum switches and hypothesis testing. In addition, quantum physics poses limitations on measurement uncertainties that are unbreakable and can hide information in quantum noise for quantum communication protocols.

This Special Issue aims to further our understanding of the features of quantum machines that allow them to surpass the capabilities of their classical counterparts by bringing together the scientific community of researchers studying quantum resource theories.

Dr. Lewis Clark
Dr. Almut Beige
Guest Editors

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• quantum correlations
• quantum Markov processes
• quantum finite-state machines
• quantum bounds
• causality
• complexity
• hypothesis testing