Correlation functions are often employed to quantify the relationships among interdependent variables or sets of data.Recently,a new class of correlation functions,called FORRELATION,has been introduced by Aaronson an...Correlation functions are often employed to quantify the relationships among interdependent variables or sets of data.Recently,a new class of correlation functions,called FORRELATION,has been introduced by Aaronson and Ambainis for studying the query complexity of quantum devices.It was found that there exists a quantum query algorithm solving 2-fold FORRELATION problems with an exponential quantum speedup over all possible classical means,which represents essentially the largest possible separation between quantum and classical query complexities.Here we report an experimental study probing the2-fold and 3-fold FORRELATIONS encoded in nuclear spins.The major experimental challenge is to control the spin fluctuation to within a threshold value,which is achieved by developing a set of optimized GRAPE pulse sequences.Overall,our small-scale implementation indicates that the quantum query algorithm is capable of determining the values of FORRELATIONS within an acceptable accuracy required for demonstrating quantum supremacy,given the current technology and in the presence of experimental noise.展开更多
1.Introduction In 1991,Rolf Landauer of IBM made his famous claim“Information is physical”[1],which clarifies that information is not just an abstract mathematical quantity,but inevitably requires a physical entity ...1.Introduction In 1991,Rolf Landauer of IBM made his famous claim“Information is physical”[1],which clarifies that information is not just an abstract mathematical quantity,but inevitably requires a physical entity to represent,transmit,process,and save.In this sense,information technology is naturally inspired and also limited by physical laws.展开更多
In this review article, we present a non-equilibrium quantum transport theory for transient electron dynamics in nanodevices based on exact Master equation derived with the path integral method in the fermion coherent...In this review article, we present a non-equilibrium quantum transport theory for transient electron dynamics in nanodevices based on exact Master equation derived with the path integral method in the fermion coherent-state representation. Applying the exact Master equation to nanodevices, we also establish the connection of the reduced density matrix and the transient quantum transport current with the Keldysh nonequilibrium Green functions. The theory enables us to study transient quantum transport in nanostructures with back-reaction effects from the contacts, with non-Markovian dissipa- tion and decoherence being fully taken into account. In applications, we utilize the theory to specific quantum transport systems, a variety of quantum decoherence and quantum transport phenomena involving the non-Markovian memory effect are investigated in both transient and stationary scenarios at arbitrary initial temperatures of the contacts.展开更多
基金supported by the National Natural Science Foundation of China(11175094,91221205,and 11405093)the National Basic Research Program of China(2015CB921002)
文摘Correlation functions are often employed to quantify the relationships among interdependent variables or sets of data.Recently,a new class of correlation functions,called FORRELATION,has been introduced by Aaronson and Ambainis for studying the query complexity of quantum devices.It was found that there exists a quantum query algorithm solving 2-fold FORRELATION problems with an exponential quantum speedup over all possible classical means,which represents essentially the largest possible separation between quantum and classical query complexities.Here we report an experimental study probing the2-fold and 3-fold FORRELATIONS encoded in nuclear spins.The major experimental challenge is to control the spin fluctuation to within a threshold value,which is achieved by developing a set of optimized GRAPE pulse sequences.Overall,our small-scale implementation indicates that the quantum query algorithm is capable of determining the values of FORRELATIONS within an acceptable accuracy required for demonstrating quantum supremacy,given the current technology and in the presence of experimental noise.
文摘1.Introduction In 1991,Rolf Landauer of IBM made his famous claim“Information is physical”[1],which clarifies that information is not just an abstract mathematical quantity,but inevitably requires a physical entity to represent,transmit,process,and save.In this sense,information technology is naturally inspired and also limited by physical laws.
文摘In this review article, we present a non-equilibrium quantum transport theory for transient electron dynamics in nanodevices based on exact Master equation derived with the path integral method in the fermion coherent-state representation. Applying the exact Master equation to nanodevices, we also establish the connection of the reduced density matrix and the transient quantum transport current with the Keldysh nonequilibrium Green functions. The theory enables us to study transient quantum transport in nanostructures with back-reaction effects from the contacts, with non-Markovian dissipa- tion and decoherence being fully taken into account. In applications, we utilize the theory to specific quantum transport systems, a variety of quantum decoherence and quantum transport phenomena involving the non-Markovian memory effect are investigated in both transient and stationary scenarios at arbitrary initial temperatures of the contacts.
