arXiv subjects

Jiang-Shan Chen

Publications and source records attributed to Jiang-Shan Chen.

6 recordsLinked to original sources

arXiv2025

Floquet composite Dirac semimetals

Dirac semimetals can be classified into types I, II, and III based on the topological charge of their Dirac points. If a three-dimensional (3D) system can be sliced into a family of kz-dependent normal and topological insulators, type I Dirac points separate a 2D normal insulator from a 2D first-order topological insulator, while type II (III) Dirac points separate a 2D normal (first-order) insulator from a 2D second-order topological insulator. To investigate the effects arising from the interplay of distinct Dirac points, one may wonder whether these Dirac points can coexist in a single system. Here, we propose a scheme to induce composite Dirac semimetals by a special Floquet driving that preserves time-reversal and space-inversion symmetries. A general description is established to characterize Dirac semimetals in Floquet systems. The results show that Dirac semimetals hosting coexisting type I, II, and III Dirac points can be induced by delta-function or harmonic driving. Our results provide a promising new avenue for exploring novel Dirac semimetals.

cond-mat.mes-hall↗

arXiv2025

Semimetals without correspondence between the topological charge of nodal line/surface and Fermi arc

It is generally believed that there is a correspondence between the topological charge of nodal points or lines and the presence of Fermi arcs. Using a $\mathcal{P}\mathcal{T}$-invariant system as an example, we demonstrate that this general belief is no longer valid. When two charged nodal lines or surfaces touch, the topological charge {dissipates without gap opening}, yet the surfaces or hinge Fermi arcs can remain preserved. It is found that both static and Floquet semimetals can exhibit Fermi arcs, even when the nodal lines or surfaces do not carry a $Z_2$ charge from second Stiefel-Whitney class.

cond-mat.mes-hall↗

arXiv2018

Experimental Realization of Sequential Weak Measurements of Arbitrary Non-commuting Pauli Observables

Sequential weak measurements of non-commuting observables is not only fundamentally interesting in quantum measurement but also shown potential in various applications. The previous reported methods, however, can only realize limited sequential weak measurements experimentally. In this Letter, we propose the realization of sequential measurements of arbitrary observables and experimentally demonstrate for the first time the measurement of sequential weak values of three non-commuting Pauli observables by using genuine single photons. The results presented here will not only improve our understanding of quantum measurement, e.g. testing quantum contextuality, macroscopic realism, and uncertainty relation, but also have many applications such as realizing counterfactual computation, direct process tomography, direct measurement of the density matrix and unbounded randomness certification.

quant-ph↗

arXiv2016

Time-invariant entanglement and sudden death of non-locality

We investigate both theoretically and experimentally the dynamics of entanglement and non-locality for two qubits immersed in a global pure dephasing environment. We demonstrate the existence of a class of states for which entanglement is forever frozen during the dynamics, even if the state of the system does evolve. At the same time non-local correlations, quantified by the violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality, either undergo sudden death or are trapped during the dynamics.

quant-ph↗

arXiv2016

Nonlocality from local contextuality

We experimentally show that nonlocality can be produced from single-particle contextuality by using two-particle correlations which do not violate any Bell inequality by themselves. This demonstrates that nonlocality can come from an {\em a priori} different simpler phenomenon, and connects contextuality and nonlocality, the two critical resources for, respectively, quantum computation and secure communication. From the perspective of quantum information, our experiment constitutes a proof of principle that quantum systems can be used simultaneously for both quantum computation and secure communication.

quant-ph↗

arXiv2016

Experimental creation of superposition of unknown photonic quantum states

As one of the most intriguing intrinsic properties of quantum world, quantum superposition provokes great interests in its own generation. Oszmaniec [Phys. Rev. Lett. 116, 110403 (2016)] have proven that though a universal quantum machine that creates superposition of arbitrary two unknown states is physically impossible, a probabilistic protocol exists in the case of two input states have nonzero overlaps with the referential state. Here we report a heralded quantum machine realizing superposition of arbitrary two unknown photonic qubits as long as they have nonzero overlaps with the horizontal polarization state $|H\rangle$. A total of 11 different qubit pairs are chosen to test this protocol by comparing the reconstructed output state with theoretical expected superposition of input states. We obtain the average fidelity as high as 0.99, which shows the excellent reliability of our realization. This realization not only deepens our understanding of quantum superposition but also has significant applications in quantum information and quantum computation, e.g., generating non-classical states in the context of quantum optics and realizing information compression by coherent superposition of results of independent runs of subroutines in a quantum computation.

quant-ph↗