02284nas a2200145 4500008004100000245007200041210006900113260001500182520181800197100001802015700002302033700001902056700002602075856003702101 2018 eng d00aElectro-optomechanical equivalent circuits for quantum transduction0 aElectrooptomechanical equivalent circuits for quantum transducti c2018/10/153 a

Using the techniques of optomechanics, a high-Q mechanical oscillator may serve as a link between electromagnetic modes of vastly different frequencies. This approach has successfully been exploited for the frequency conversion of classical signals and has the potential of performing quantum state transfer between superconducting circuitry and a traveling optical signal. Such transducers are often operated in a linear regime, where the hybrid system can be described using linear response theory based on the Heisenberg-Langevin equations. While mathematically straightforward to solve, this approach yields little intuition about the dynamics of the hybrid system to aid the optimization of the transducer. As an analysis and design tool for such electro-optomechanical transducers, we introduce an equivalent circuit formalism, where the entire transducer is represented by an electrical circuit. Thereby we integrate the transduction functionality of optomechanical (OM) systems into the toolbox of electrical engineering allowing the use of its well-established design techniques. This unifying impedance description can be applied both for static (DC) and harmonically varying (AC) drive fields, accommodates arbitrary linear circuits, and is not restricted to the resolved-sideband regime. Furthermore, by establishing the quantized input/output formalism for the equivalent circuit, we obtain the scattering matrix for linear transducers using circuit analysis, and thereby have a complete quantum mechanical characterization of the transducer. Hence, this mapping of the entire transducer to the language of electrical engineering both sheds light on how the transducer performs and can at the same time be used to optimize its performance by aiding the design of a suitable electrical circuit.

1 aZeuthen, Emil1 aSchliesser, Albert1 aTaylor, J., M.1 aSørensen, Anders, S. uhttps://arxiv.org/abs/1710.1013604684nas a2200145 4500008004100000245004500041210004500086260001500131520426900146100001804415700002304433700002604456700001904482856003704501 2016 eng d00aFigures of merit for quantum transducers0 aFigures of merit for quantum transducers c2016/10/043 a

Recent technical advances have sparked renewed interest in physical systems that couple simultaneously to different parts of the electromagnetic spectrum, thus enabling transduction of signals between vastly different frequencies at the level of single photons. Such hybrid systems have demonstrated frequency conversion of classical signals and have the potential of enabling quantum state transfer, e.g., between superconducting circuits and traveling optical signals. This Letter describes a simple approach for the theoretical characterization of performance for quantum transducers. Given that, in practice, one cannot attain ideal one-to-one quantum conversion, we will explore how well the transducer performs in various scenarios ranging from classical signal detection to applications for quantum information processing. While the performance of the transducer depends on the particular application in which it enters, we show that the performance can be characterized by defining two simple parameters: the signal transfer efficiency η and the added noise N.

1 aZeuthen, Emil1 aSchliesser, Albert1 aSørensen, Anders, S.1 aTaylor, J., M. uhttps://arxiv.org/abs/1610.01099