Remote Hamiltonian interactions mediated by light

Abstract

We address a fundamental question of quantum optics: Can a beam of light mediate coherent Hamiltonian interactions between two distant quantum systems? This is an intriguing question whose answer is not a priori clear, since the light carries away information about the systems and might be subject to losses, giving rise to intrinsic decoherence channels associated with the coupling.Our answer is affirmative and we derive a particularly simple sufficient condition for the interactions to be Hamiltonian: The light field needs to interact twice with the systems and the second interaction has to be the time reversal of the first.We demonstrate that, even in the presence of significant optical loss, coherent interactions can be realized and generate substantial amounts of entanglement between the systems. Our method is directly applicable for building hybrid quantum systems, with relevant applications in the fields of optomechanics and atomic ensembles. * thomas.karg@unibas.ch † philipp.treutlein@unibas.ch framework was applied fruitfully in the description of cascaded optical cavities [8], atomic ensembles interacting arXiv:1901.06891v2 [quant-ph]

Collisional picture of quantum optics with giant emitters

“…This condenses in a single equation and extends a variety of master equations used in waveguide QED [40,[48][49][50], as will be illustrated in detail. Moreover, we show that the recently discovered possibility to realize decoherence-free Hamiltonians with giant emitters [46,51] is naturally predicted in the collisional picture, without the need to resort to the master equation, thus highlighting its independence of the field state. Additionally, for an arbitrary photodetection scheme, we calculate the Kraus operators corresponding to a measurement outcome and use these to derive the effective Hamiltonian and jump operators generating the quantum trajectories.…”

“…For a bidirectional field (see Sec. II B), unitariesÛ t andÛ n are formally the same as (46) and (47), respectively, butV t is now given by Eq. (12).…”

“…fields in looped geometries [44,45] as explicitly discussed in Ref. [46]. The framework is first formulated by considering a unidirectional field (just like in the standard input-output formalism [47]) and then extended to a bidirectional field.…”

“…In Eq (46). we neglect the contribution coming from the interval between [t/ t] t and t since this vanishes in the limit t → 0.…”

Pulsed atom-mechanical quantum non-demolition gate

“…8 As a resource to reduce noise in stationary hybrid systems, steady-state entanglement in hybrid atom-optomechanical systems and different coupling schemes is sufficient. 6,18,[31][32][33][34] However, hybrid quantum processing requires specific types of pulsedcontrolled hybrid gates which is the challenging next step. Such gates will operate on quantum states of matter resolved in time, which is necessary to process quantum information.…”