Quantum noise in the electromechanical shuttle: Quantum master equation treatment

Abstract

We investigate the use of nanocrystal quantum dots as a quantum bus element for preparing various quantum resources for use in photonic quantum technologies. Using the Stark-tuning property of nanocrystal quantum dots as well as the biexciton transition, we demonstrate a photonic controlled-NOT ͑CNOT͒ interaction between two logical photonic qubits comprising two cavity field modes each. We find the CNOT interaction to be a robust generator of photonic Bell states, even with relatively large biexciton losses. These results are discussed in light of the current state of the art of both microcavity fabrication and recent advances in nanocrystal quantum dot technology. Overall, we find that such a scheme should be feasible in the near future with appropriate refinements to both nanocrystal fabrication technology and microcavity design. Such a gate could serve as an active element in photonic-based quantum technologies.

Single molecular shuttle-junction: Shot noise and decoherence

“…Furthermore, the master equation can equally consider the tunneling and dissipation terms, unlike early derivations, which required treating these terms separately [36,43,85]. In the low temperature and high bias voltage regime, the presented master equation should agree with those given previously [3,36].…”

“…Therefore, the theory of an open system, such as the master equation, is suitable for describing electron transport. In fact, the master equation has been widely applied in the area of transport materials [3,28,[111][112][113][114]. In this section, we introduce a typical shuttle-junction model and develop a quantum master equation to discuss properties of single molecular shuttle-junctions.…”

“…Such system are also known as shuttle-junctions. In the semiclassical regime, time evolution of the shuttle-junction shows electron transfer one-by-one orderly [2,3]. Furthermore, the tunneling-position coupling in the electromechanical junction has significant applications in the detection of displacement [4][5][6][7], spin [8,9], charge [10,11], and mass [12].…”

“…In a fully quantum mechanical description of the electromechanical process [43], the coherent coupling is included at the cost of solving a large matrix in the mathematical treatment. The quantum mechanical model of the coherent dynamics is further developed to investigate the shuttling mechanism [3,36,37]. According to the charge-position (momentum) correlation, the motion of the quantum shuttle can be described by the shuttling and tunneling regimes as well as the coexistence of these regimes [2,36].…”

“…In the shuttling regime, the electron transport is highly deterministic and characterized by the extraordinary sub-Poissonian Fano factor [37]. By measuring the shot noise, the transition between tunneling and shuttling can be identified [3]. Moreover, single molecular vibrational junctions have recently been studied in strong correlation physics such as the Kondo effect [44][45][46][47][48], pair tunneling, and co-tunneling [49,50].…”