Fundamental limits of energy dissipation in charge-based computing

Abstract

According to Landauer’s principle, dissipation of energy is only necessary when information is erased, suggesting that vastly more efficient logical switches than transistors are possible. However, an influential analysis of binary switching suggests that representing information with electric charge is the root of the problem, that Landauer’s principle is fundamentally flawed, and that any movement of charge, such as charging a capacitor, must dissipate at least kBT ln(2). Here, using a RC circuit, an energy loss of much less than kBT ln(2) is demonstrated while delivering energy of 100 kBT ln(2) to the capacitor. This shows that there is no fundamental lower limit to energy dissipation in moving charge.

Quantum Landauer erasure with a molecular nanomagnet

“…The performance of our spin register in terms of energy-time cost is orders of magnitude better than existing memory devices to date. The result shows that thermodynamics sets a limit on the energy cost of certain quantum operations and illustrates a way to enhance classical computations by using a quantum system.While a computation performed with an ideal binary logic gate (for example, NOT) has no lower energy dissipation limit [5][6][7] , one carried out in a memory device does. The reason is that in the former the bit is merely displaced isentropically in the space of states, whereas in the latter the minimal operation, called Landauer erasure, entails resetting the memory irrespective of its initial state.…”

Response to “Comment on ‘Fundamental limits of energy dissipation in charge-based computing’ ” [Appl. Phys. Lett. 98, 096101 (2011)]

“…6 show by direct measurement that a capacitor can in fact be charged and discharged adiabatically. The energy stored on the capacitor can be much larger than k B T log͑2͒ while the dissipated energy is much less than k B T log͑2͒.…”

“…6 to show how adiabatic switching could be employed in specific systems; we have done that elsewhere. 2 Our goal in Ref.…”

“…In our letter 6 we did not address issues of the power dissipation in the signal generator, choosing instead to focus on an experimental test of ZC's clear assertion of a dissipation limit in adiabatic charging. 5,8 The clock generators are not fundamental to the issue at hand.…”

“…2 Our goal in Ref. 6 was to address specific claims made by ZC regarding fundamental limits of dissipation in charge-based devices.…”