Irreversible logic operations inevitably discard information, setting fundamental limitations on the flexibility and the efficiency of modern computation. To circumvent the limit imposed by the von Neumann-Landauer (VNL) principle, an important objective is the development of reversible logic gates, as proposed by Fredkin, Toffoli, Wilczek, Feynman, and others. Here, we present a novel nanomechanical logic architecture for implementing a Fredkin gate, a universal logic gate from which any reversible computation can be built. In addition to verifying the truth table, we demonstrate operation of the device as an AND, OR, NOT, and FANOUT gate. Excluding losses due to resonator dissipation and transduction, which will require significant improvement in order to minimize the overall energy cost, our device requires an energy of order 10(4) kT per logic operation, similar in magnitude to state-of-the-art transistor-based technologies. Ultimately, reversible nanomechanical logic gates could play a crucial role in developing highly efficient reversible computers, with implications for efficient error correction and quantum computing.

We present measurements of nonlinear coupling between various acoustic modes of a micromechanical resonator. Piezoelectric transduction allows measurement of both flexural and bulk longitudinal modes up to microwave frequencies, and we find that all modes of the device couple, regardless of type. This coupling thus provides a means of mechanical nonlinear signal processing across a wide range of frequencies. Through controlled simultaneous excitation, we quantify coupling strength by measuring the frequency shift in a detector mode in response to the known energy of a driven mode.

We demonstrate the fabrication and operation of an integrated device containing a nanoelectromechanical system and an integrated detector. This on-chip silicon nanochannel field effect transistor is used to measure the motion of a silicon nanomechanical resonator at room temperature. Furthermore, we describe the operation of the device as a silicon-based room-temperature on-chip amplifier for improved displacement detection of nanomechanical resonators.

We report measurements of Aharonov-Bohm oscillations in normal metal rings in the presence of high frequency electromagnetic fields. The power dependence of the decoherence time scale τ φ (P ) agrees well with the anticipated power law τ φ ∝ P −1/5 when the field-induced decoherence rate τ −1 ac is large compared to the intrinsic decoherence rate τ −1 o , measured in the absence of external fields. As theoretically expected, we observe a decline in field-induced decoherence when τ −1 ac ≤ τ −1 o . The frequency dependence of τ φ shows a minimum in the oscillation amplitude at a characteristic frequency, ωac 1/τo, where τo is evaluated from the oscillation amplitude using the standard mesoscopic theory. Both the suppression in the oscillation amplitude and the concomitant change in conductivity allow a direct measurement of the intrinsic decoherence time scale.