Operating micromechanical logic gates below kBT: Physical vs logical reversibility

Summary form only given. In modern computers computation is performed by assembling together sets of logic gates made by transistors acting as logic switches. The scaling of transistor dimensions allowed a continuous increase of performance accompanied by an increase of heat production. The latter will represent a road-block for the development of future computing devices. Landauer theorized on the minimum heat production required to perform a reset operation of one bit, i.e. Q
_L
=k
_B
Tlog2, a result that has been recently experimentally shown by S. Ciliberto et al. However, a question that is still somehow controversial is the following: is there a finite minimum amount of energy required to operate an irreversible logic gate? In the following a logically irreversible operation is implemented by means of a MEMS cantilever actuated by two electrostatic probes. The voltages on the probes represent the logical input to the gate. The output of the logic gate is encoded in the position of the cantilever. By setting appropriately the threshold of the logical states the system is able to perform the logic AND or OR gate. The implementation of the logic gate is logically irreversible since from the sole knowledge of the output state it is not possible to recover the configuration of the input forces. In particular, `01' and `10' input states gives the same output value.