Dirac Equation — Zitterbewegung

Trembling motion of free relativistic electron • Interference of positive/negative energy states
1.0
0.50
3.0
1.0
⟨x⟩ position
ZB frequency ω_ZB
ZB amplitude
Group velocity v_g
ZB: ⟨x⟩(t) = v_g·t + (ℏ/(2mc))·sin(2mc²t/ℏ)·(positive/neg. energy interference)  |  ω_ZB = 2mc²/ℏ
Zitterbewegung ("trembling motion") is a rapid oscillation predicted by the Dirac equation for free electrons, arising from interference between positive and negative energy components of the wavepacket. Frequency ω = 2mc²/ℏ ≈ 1.55×10²¹ Hz — too fast to observe directly, but analog systems (trapped ions, graphene) simulate it.