Protecting entanglement by adjusting the velocities of moving qubits inside non-Markovian environments

Abstract

Efficient entanglement preservation in open quantum systems is a crucial scope towards a reliable exploitation of quantum resources. We address this issue by studying how two-qubit entanglement dynamically behaves when two atom qubits move inside two separated identical cavities. The moving qubits independently interact with their respective cavity. As a main general result, we find that under resonant qubit-cavity interaction the initial entanglement between two moving qubits remains closer to its initial value as time passes compared to the case of stationary qubits. In particular, we show that the initial entanglement can be strongly protected from decay by suitably adjusting the velocities of the qubits according to the non-Markovian features of the cavities. Our results supply a further way of preserving quantum correlations against noise with a natural implementation in cavity-QED scenarios and are straightforwardly extendable to many qubits for scalability.

Validating and controlling quantum enhancement against noise by the motion of a qubit

“…(1), a † k (a k ) denotes the creation (annihilation) operator for the k-th cavity mode with frequency ω k and g k is the coupling constant between the qubit and the k-th mode. The parameter f k (z) describes the shape function of qubit motion along the z-axis, and it is given by [50][51][52] (2) where β = v/c, c being the speed of light. It is evident that the coupling function will be nonzero for z = 0 and zero for z = l (perfect boundary).…”

“…It is worth mentioning that the translational motion of an atom can be considered classical (z = vt) as long as the de Broglie wavelength λ B of the atom is much smaller than the wavelength λ 0 of the resonant transition (λ B /λ 0 1) [50][51][52][53]. Moreover, the relative smallness of photon momentum ( ω 0 /c) compared to atomic momentum (mv) allows one to neglect the atomic recoil resulting from the interaction with the electric field [54].…”

Scalable quantum computing model in the circuit-QED lattice with circulator function

“…Here the effective potential minimum decreases until the output current I 2 reaches the maximum value, −I 1 , which can also be seen from the relation ∂U eff,min (I 2 )/∂I 2 = (Φ 0 /2π)(φ +,min + φ −,min ) ≈ Φ 0 /6 > 0 with the effective potential in Eq. (12). This means that the input current I 1 from the j = 1 resonator flows through only j = 2 resonator (I 2 = −I 1 ) while there is no output current flowing through the j = 3 resonator (I 3 = 0).…”

“…Owing to the remarkable advancements in the qubit (quantum bit) coherence and control the scalable and programmable quantum computing is expected to be realized in the near future [1,2,3,4,5,6,7,8,9,10,11,12,13]. A large scale quantum computer consisting of many qubits integrated may perform quantum algorithms capable of carrying out tasks that are hard or impossible for ordinary classical computer.…”

Coherence and entanglement dynamics of vibrating qubits

“…The simplest situation of atom-photon interaction is that of a two-level atom inside a cavity sustaining a single electromagnetic field mode, described by the famous Jaynes-Cummings Hamiltonian [20]. In this context, it is well known that the coupling of an atom to the cavity field is position-dependent, which in turn makes the atom-field coupling for a moving atom qubit time dependent [21,22]. Recent developments in cavity quantum electrodynamics (QED) setups offer the possibility to trap an ion inside a cavity [23,24].…”