Measurement Quench in Many-Body Systems

Abstract

Measurement is one of the key concepts which discriminates classical and quantum physics. Unlike classical systems, a measurement on a quantum system typically alters it drastically as a result of wave function collapse. Here we suggest that this feature can be exploited for inducing quench dynamics in a many-body system while leaving its Hamiltonian unchanged. Importantly, by doing away with dedicated macroscopic devices for inducing a quench-using instead the indispensable measurement apparatus only-the protocol is expected to be easier to implement and more resilient against decoherence. By way of various case studies, we show that our scheme also has decisive advantages beyond reducing decoherence-for spectroscopy purposes and probing nonequilibrium scaling of critical and quantum impurity many-body systems. DOI: 10.1103/PhysRevLett.121.030601 Introduction.-Measurement is a fundamental concept that discriminates between the classical and quantum worlds. While in the classical regime measurement is noninvasive with no effect on the system, in the quantum domain, however, acquiring information, even through a local measurement, comes at the cost of an abrupt wavefunction collapse that affects the entire system. The fundamental tests for the validity of quantum mechanics, such as the violation of Bell [1,2] and Legett-Garg [3] inequalities are based on quantum measurements. Moreover, they are crucial ingredients of almost all emerging quantum technologies such as quantum teleportation [4], measurementbased quantum computation [5], fault-tolerant quantum computation [6] and spin-chain quantum communication [7][8][9].All quantum protocols consist of preparation, manipulation, and readout of one or more particles. While preparation and manipulation can be achieved by different means, the readout is unequivocally accomplished by measurements. Experimentally, these all rely on macroscopic devices which may induce decoherence and increase the complexity of the process. This raises the following question: Is it possible to simplify the whole process by keeping only the indispensable part of the macroscopic devices, i.e., the measurement apparatus, for the complete preparation and manipulation of the system?To answer the question, one should first recall that a key task of any quantum protocol is to induce the "right" kind of dynamics on a system. A particularly important class is that of quench dynamics, where the time evolution is induced in

Bethe Ansatz for XXX chain with negative spin

“…The Fermi velocity v F (also known as quench velocity v e for local quenches [12,13]) can be defined as…”

“…In the Euclidian formulation, the correlation functions depend on |x + iv F t|, where x and t are space and time, see Chapter XVIII Section 2 of the book [4]. The Fermi velocity v F coincides with v e , the velocity of the spread of entanglement entropy after a measurement quench, see [13].…”

Integrable quantum many-body sensors for AC field sensing

“…In fact, thanks to the emergent of multipartite entanglement [63][64][65][66][67][68], many-body systems near criticality provide enhanced quantum precision of η = 2/ν [50][51][52][53][54][55], where ν is the critical exponent in charge of the divergence of correlation length [69,70]. In addition, the evolution of many-body systems has also been used for sensing local [62] and global [71] DC fields as well as extracting information about the spectral structure of time-varying fields [72][73][74]. In most of these works, either static or dynamic, it is dominantly assumed that the whole system is accessible for measurement which may not be practical.…”

Dynamical Quantum Phase Transitions in the 1D Nonintegrable Spin‐1/2 Transverse Field XZZ Model

“…[2,3] This has led to the observation of many-body localization and prethermalization, [4][5][6][7][8] time crystals, [9][10][11] momentum-time skyrmions, [12] and dynamics in gauge theories. [13,14] In analog to some approaches such as the Kibble-Zurek mechanism [15] and measurement quench, [16,17] in recent years, the theory of dynamical quantum phase transition (DQPT) manifested with nonanalytic behaviors of the rate function in the time domain, that is, the logarithm function of the Loschmidt echo (LE), has attracted tremendous attention. [20][21][22][23][24][25][26][27][28][29] DQPT is established by borrowing the idea from equilibrium statistical mechanics.…”