Study On Recovering And Applications Of Quantum Resources

In recent years,quantum information science has made excellent progress,showing a series of characteristics that are different from classical physics.Quantum resource theory provides a useful theoretical framework for quantum information.However,quantum resources are rare and perishable,which makes them precious.Therefore,it is significant to study how to obtain and preserve quantum resources in quantum information and quantum computation.This thesis focuses on the research of quantum resources.From the perspective of identification,protection,and applications of quantum resources,we divide this thesis into four main parts:First of all,violation of Bell inequality becomes the necessary and sufficient criteria to detect entanglement in pure bipartite states.And thus,it is important to study the upper bound of Bell inequality for the identification of entangled states.Recently,researchers have constructed the Bell-type inequality of product states for l₁-norm of coherence and found that the maximally entangled states can violate it.we investigate the Bell-type inequalities of l₁-norm of coherence for two or three-qubit system and establish the relation between the l₁-norm of coherence and the degree of coherence.It is found that the upper bounds of the inequalities can be much stronger.The Bell-type inequality of l₁-norm of coherence for two-qubit system can be violated by all two-qubit entangled pure states.The Bell-type inequalities can also be violated by quantum systems which pass through the uncorrelated or correlated channels.Particularly,the partial correlations among consecutive uses of the correlated channel can enhance the value of the left-hand side of the Bell-type inequalities.The Bell-type inequality constructed by us can be better used to identify quantum entanglement.Then,quantum system will be disturbed due to the inevitable interaction between the quantum system and its surrounding environment.The previous studies about the partial correlations of the channel focus on qubit systems.High dimensional quantum systems have significant advantages in quantum information and quantum computing.Thus,we investigate the dynamics of a two-qutrit system in a correlated quantum channel.The partial correlations between consecutive actions of the channel can effectively postpone the phenomenon of distillability sudden death(DSD)and broaden the range of the time cutoff that indicates entanglement of the positive partial transpose states.Particularly,the negativity of the system will revive and DSD will disappear in the fully correlated channel.Furthermore,nonlocal advantage of quantum coherence(NAQC)will also dissipate unnecessarily due to the coupling between quantum system and environment.The previous studies mostly focus on qubits system,and NAQC for qutrits system is seldom exploited.Therefore,we consider the scheme to recover NAQC for two-qutrit system which suffer from the amplitude damping noises by using weak measurement reversal.The scope of the decay rate of the noise to achieve NAQC can be obviously extended after the application of weak measurement reversal,i.e.NAQC can be recovered in the region that there is no NAQC.The physical reason for the recovery may be attributed to the probabilistic nature of the scheme as well as the shrinking of the range for the state parameter to achieve NAQC.In the end,quantum coherence and NAQC have been adopted to identify quantum phase transition point.However,the critical behaviors at quantum phase transition point for the spin system with multipartite interaction have not been detected by quantum coherence or NAQC.Therefore,we investigate the performance of quantum coherence and NAQC for the central spin-1 system which couples to an XY spin chain with three-spin interaction in a transverse magnetic field.For the case that the central spin system couple weakly to the spin chain,both quantum coherence and NAQC endure sudden change around the critical point of quantum phase transitions when the three-spin interaction is switched off.While there is three-spin interaction,the performances of quantum coherence and NAQC indicate that the critical point has been shifted away from its ordinary position.Therefore,quantum coherence and NAQC can be used to detect the critical point of quantum phase transitions of the XY spin chain for the weak-coupling case.However,three-spin interaction has no obvious effect on the dynamics of quantum coherence and NAQC for the strong-coupling case.This thesis has 17 figures and 193 references...