Quantum Nyquist temperature fluctuations

Using the Nyquist approach, temperature fluctuations of an object, in thermal contact with a reservoir, are studied. We argue that, upon decreasing the size of the object, one necessarily reaches the quantum regime. The crossover temperature between the classical and quantum regimes is given by View the MathML source, where τ is the thermal relaxation time of the system. For a nano-scale metallic particle in a good thermal contact with a reservoir, T∗ can be on a scale of a few Kelvin.