<P> Virtual particles with negative energy can exist for a short period . This phenomenon is a part of the mechanism involved in Hawking radiation by which black holes evaporate . </P> <P> It is possible to arrange multiple beams of laser light such that destructive quantum interference suppresses the vacuum fluctuations . Such a squeezed vacuum state involves negative energy . The repetitive waveform of light leads to alternating regions of positive and negative energy . </P> <P> According to the theory of the Dirac sea, developed by Paul Dirac in 1930, the vacuum of space is full of negative energy . This theory was developed to explain the anomaly of negative - energy quantum states predicted by the Dirac equation . </P> <P> The Dirac sea theory correctly predicted the existence of antimatter two years prior to the discovery of the positron in 1932 by Carl Anderson . However, the Dirac sea theory treats antimatter as a hole where there is the absence of a particle rather than as a real particle . Quantum field theory (QFT), developed in the 1930s, deals with antimatter in a way that treats antimatter as made of real particles rather than the absence of particles, and treats a vacuum as being empty of particles rather than full of negative - energy particles like in the Dirac sea theory . </P>

What does it mean to have negative energy