Nonequilibrium Current Noise Spectrum in a Dissipative Conductor

We study the noise spectrum of electrical current in a voltage-biased conductor. At low frequencies, the noise power in a nondissipative conductor is below the standard quantum limit which typically appears in tunnel junctions. Energy dissipation in the conductor further reduces the low-frequency noise power, nearly to zero when the dissipation is strong enough. At high frequencies, however, the noise is no longer suppressed, and the noise power approaches the standard quantum limit irrespective of the strength of energy dissipation.