Josephson Constant

The frequency-per-volt of the AC Josephson effect: 483.6 THz per volt, the quantum volt standard.

Specifications & Metrics

symbol

KJ

status

Exact — fixed by the 2019 SI (e and h are exact)

value

483597848400000 Hz·V⁻¹

Relative Scale in Constants

Core Principles & Analysis

• Exactly 2e/h; practical volt standards realize it with arrays of junctions.
• A microwave-irradiated junction switches at precisely known voltage steps.
• Since 1990 the world's volt has been defined through it.