A von-Neumann-like photonic processor and its application in studying quantum signature of chaos

Photonic quantum computation plays an important role and offers unique advantages.Two decades after the milestone work of Knill-Laflamme-Milburn,various architectures of photonic processors have been proposed,and quantum advantage over classical computers has also been demonstrated.It is now the opportune time to apply this technology to real-world applications.However,at current technology level,this aim is restricted by either programmability in bulk optics or loss in integrated optics for the existing architectures of processors,for which the resource cost is also a problem.Here we present a von-Neumann-like architecture based on temporal-mode encoding and looped structure on table,which is capable of multimode-universal programmability,resource-efficiency,phasestability and software-scalability.In order to illustrate these merits,we execute two different programs with varying resource requirements on the same processor,to investigate quantum signature of chaos from two aspects:the signature behaviors exhibited in phase space(13 modes),and the Fermi golden rule which has not been experimentally studied in quantitative way before(26 modes).The maximal program contains an optical interferometer network with 1694 freely-adjustable phases.Considering current state-of-the-art,our architecture stands as the most promising candidate for real-world applications.

Experimental verification of generalized eigenstate thermalization hypothesis in an integrable system

Identifying the general mechanics behind the equilibration of a complex isolated quantum system towards a state described by only a few parameters has been the focus of attention in non-equilibrium thermodynamics.And several experimentally unproven conjectures are proposed for the statistical description of quantum(non-)integrable models.The plausible eigenstate thermalization hypothesis(ETH),which suggests that each energy eigenstate itself is thermal,plays a crucial role in understanding the quantum thermalization in non-integrable systems;it is commonly believed that it does not exist in integrable systems.Nevertheless,integrable systems can still relax to the generalized Gibbs ensemble.From a microscopic perspective,understanding the origin of this generalized thermalization that occurs in an isolated integrable system is a fundamental open question lacking experimental investigations.Herein,we experimentally investigated the spin subsystem relaxation in an isolated spin-orbit coupling quantum system.By applying the quantum state engineering technique,we initialized the system with various distribution widths in the mutual eigenbasis of the conserved quantities.Then,we compared the steady state of the spin subsystem reached in a long-time coherent dynamics to the prediction of a generalized version of ETH and the underlying mechanism of the generalized thermalization is experimentally verified for the first time.Our results facilitate understanding the origin of quantum statistical mechanics.