The Landauer’s principle links information theory and thermodynamics, as it sets a lower bound for the energy required to manipulate a memory system. It states that any logically irreversible transformation of information is accompanied by the dissipation of at least k_B T ln 2 of heat per bit operated, where k_B is the Boltzmann constant and T is the temperature. An operation is said to be logically irreversible if its input cannot be uniquely determined from its output. For example an erasure of information, where one bit (that can be either 0 or 1) is reset to the 0 state, is logically irreversible and leads to a heat release of at least k_B T ln 2 per erased bit. This quantity is very small: it represents only 3 × 10^−21 J at room temperature, but it can be reached in small systems where thermal fluctuations play an important role. In this seminar we will describe an experimental realization of the “Landauer’s erasure protocol” with a silica micro-particle held in a double-well potential created by optical tweezers. In this system where fluctuations cannot be neglected, the heat dissipated is computed in the framework of stochastic thermodynamics. We will show that the limit can only be reached if the procedure is slow enough (i.e. in the quasi-static limit), and that a detailed Jarzynski equality allows to retrieve the Landauer limit independtly of the procedure’s speed.
Institut Universitaire des Systèmes Thermiques Industriels (IUSTI)