arXiv subjects

Yu-Chien Kao

Publications and source records attributed to Yu-Chien Kao.

3 recordsLinked to original sources

arXiv2024

Preparing Remote States for Genuine Quantum Networks

Quantum networks typically comprise quantum channels, repeaters, and end nodes. Remote state preparation (RSP) allows one end node to prepare the states of the other end nodes remotely. While quantum discord has recently been recognized as necessary for RSP, it does not guarantee the practical implementation of RSP in quantum networks surpasses any classical method. Herein, we theoretically introduce and experimentally study a quantum resource that we call the RSP capability. This resource validates all the static and dynamic elements required to enable genuine quantum networks where the RSP's implementation can outperform any classical emulation of entanglement- and qubit-unitaries-free strategies, including the static resources of Einstein-Podolsky-Rosen pairs and the dynamic resources of quantum channels and repeaters. Our experiment measures the RSP capability to demonstrate the transition between classical and nonclassical RSP depending on the photon-pair qualities. It shows that quantum discord does not confirm a nonclassical RSP, but the RSP capability does. These results help reveal the quantum advantages that emerge when networking RSP is in play.

quant-ph↗

arXiv2024

Photonic non-Markovianity identification by quantum process capabilities of non-CP processes

A Markovian quantum process can be arbitrarily divided into two or more legitimate completely-positive (CP) subprocesses. When at least one non-CP process exists among the divided processes, the dynamics is considered non-Markovian. However, how to utilize minimum experimental efforts, without examining all process input states and using entanglement resources, to identify or measure non-Markovianity is still being determined. Herein, we propose a method to quantify non-CP processes for identifying and measuring non-Markovianity without the burden of state optimization and entanglement. This relies on the non-CP processes as new quantum process capabilities and can be systematically implemented by quantum process tomography. We additionally provide an approach for witnessing non-Markovianity by analyzing at least four system states without process tomography. We faithfully demonstrate that our method can be explicitly implemented using all-optical setups and applied to identify the non-Markovianity of single-photon and two-photon dynamics in birefringent crystals. Our results can also be used to explore non-Markovianity in other dynamical systems where process or state tomography is implementable.

quant-ph↗

arXiv2020

Nonclassical Preparation of Quantum Remote States

Remote state preparation (RSP) enables a sender to remotely prepare the quantum state of a receiver without sending the state itself. Recently, it has been recognized that quantum discord is a necessary resource for RSP. Here, we theoretically and experimentally investigate whether RSP can outperform dynamic classical remote state preparation processes. We show that such classical processes can describe certain RSPs powered by quantum discord. Rather, we argue that a new kind of Einstein-Podolsky-Rosen steering for dynamical processes, called quantum process steering, is the resource required for performing nonclassical RSP. We show how to measure quantum process steering by experimentally realizing nonclassical RSP of photonic quantum systems. Moreover, we demonstrate the transition from classical to quantum RSP. Our results also have applications in realizing genuine quantum RSP for quantum-enabled engineering.

quant-ph↗