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kBTln⁡2=(1.380649×10−23 JK)(300 K)(0.6931)≈2.87×10−21 J≈2.9 zJk_B T \ln 2 = \left(1.380649\times10^{-23}\ \tfrac{\text{J}}{\text{K}}\right)(300\ \text{K})(0.6931) \approx 2.87\times10^{-21}\ \text{J} \approx 2.9\ \text{zJ}

Why this formula appears here

where kBk_B is Boltzmann’s constant. At room temperature — 300 kelvin, a reasonable stand-in for a chip’s operating temperature — plugging in Boltzmann’s constant’s exact SI value gives: kBTln⁡2=(1.380649×10−23 JK)(300 K)(0.6931)≈2.87×10−21 J≈2.9 zJk_B T \ln 2 = \left(1.380649\times10^{-23}\ \tfrac{\text{J}}{\text{K}}\right)(300\ \text{K})(0.6931) \approx 2.87\times10^{-21}\ \text{J} \approx 2.9\ \text{zJ}. That bound is not a rough estimate awaiting refinement; it has been directly tested. A 2012 experiment reported in Nature, using a colloidal silica bead trapped in an optical potential rather than an electronic circuit, measured the heat dissipated while erasing one bit of information stored in the bead’s position and found it consistent with the Landauer bound within experimental uncertainty in the low-erasure-rate limit, the first experiment to test the bound this directly at the…

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kBTln⁡2=(1.380649×10−23 JK)(300 K)(0.6931)≈2.87×10−21 J≈2.9 zJk_B T \ln 2 = \left(1.380649\times10^{-23}\ \tfrac{\text{J}}{\text{K}}\right)(300\ \text{K})(0.6931) \approx 2.87\times10^{-21}\ \text{J} \approx 2.9\ \text{zJ}

Equation 4 · Technological Evolution

After Moore: The Adaptive Radiation of Compute

This equation gives an approximation: it relates the quantities while allowing an approximation.

where kBk_B is Boltzmann’s constant. At room temperature — 300 kelvin, a reasonable stand-in for a chip’s operating temperature — plugging in Boltzmann’s constant’s exact SI value gives: kBTln⁡2=(1.380649×10−23 JK)(300 K)(0.6931)≈2.87×10−21 J≈2.9 zJk_B T \ln 2 = \left(1.380649\times10^{-23}\ \tfrac{\text{J}}{\text{K}}\right)(300\ \text{K})(0.6931) \approx 2.87\times10^{-21}\ \text{J} \approx 2.9\ \text{zJ}. That bound is not a rough estimate awaiting refinement; it has been directly tested. A 2012 experiment reported in Nature, using a colloidal silica bead trapped in an optical potential rather than an electronic circuit, measured the heat dissipated while erasing one bit of information stored in the bead’s position and found it consistent with the Landauer bound within experimental uncertainty in the low-erasure-rate limit, the first experiment to test the bound this directly at the…

Meanings in this article

  • TT: the absolute temperature.
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