Abstract
Coherent quantum control over many-particle quantum systems requires high fidelity dynamics. One way of achieving this is to use adiabatic schemes where the system follows an instantaneous eigenstate of the Hamiltonian over timescales that do not allow transitions to other states. This, however, makes control dynamics very slow. Here we introduce another concept that takes advantage of preventing unwanted transitions in fermionic systems by using Pauli blocking: excitations from a protected ground state to higher-lying states are avoided by adding a layer of buffer fermions, such that the protected fermions cannot make a transition to higher lying excited states because these are already occupied. This allows to speed-up adiabatic evolutions of the system. We do a thorough investigation of the technique, and demonstrate its power by applying it to high fidelity transport, trap expansion and splitting in ultracold atoms systems in anharmonic traps. Close analysis of these processes also leads to insights into the structure of the orthogonality catastrophe phenomenon.
Highlights
Preparation of and coherent control over many-particle quantum states require quantum-engineering techniques that lead to high fidelities
This, makes control dynamics very slow. We introduce another concept that takes advantage of preventing unwanted transitions in fermionic systems by using Pauli blocking: excitations from a protected ground state to higher-lying states are avoided by adding a layer of buffer fermions, such that the protected fermions cannot make a transition to higher-lying excited states because these are already occupied
Adiabatic processes, where the system follows an eigenstate of the time-dependent Hamiltonian, are known to allow for this; they require that the Hamiltonian be varied sufficiently slowly in order to avoid transitions to other eigenstates [1]
Summary
Preparation of and coherent control over many-particle quantum states require quantum-engineering techniques that lead to high fidelities. Freedom increases exponentially with larger particle numbers The effects of this are well known and can be seen immediately when considering one of the most simple systems possible, namely an ideal, spin-polarized, one-dimensional Fermi gas at low temperatures: even in the presence of almost perfect single-particle process fidelities, the overlap between two many-particle wave functions scales with N −α, where α depends on the specific nature of the change between the initial and final Hamiltonian [11]. Since the technique we discuss below will protect the lower motional energy states, and since the protection is done by the presence of a Fermi sea, it requires fermionic samples that are deep within the quantum degenerate regime For neutral atoms these can be produced routinely in laboratories worldwide these days [26,27,28], and since the removal of the higher energy particles from a trap can be done using standard techniques, we will concentrate in this paper on the control process itself.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
