Quantum fissure

From Memory Alpha, the free Star Trek reference

A Quantum fissure is a quantum anomaly in the space-time continuum. In a sealed state the anomaly remained undetected and presented no threat to the continuum. A fissure discovered in 2370 near Forcas III was a fixed point intersecting several alternate quantum realities.

The warp engines of a ship traveling through a quantum fissure could accidentally cause a small break in the barriers between quantum realties. When the barriers were weakened in this way, the anomaly appeared as an invisible minor subspace disturbance. A weakened fissure could be made visible by a warp field. Occupants of the traversing ship were thrown into a state of quantum flux and exchanged their consciousness with their counterparts in another random quantum reality. A subspace field pulse, such as the one emitted by an active VISOR, encountered by an individual in a state of quantum flux would intensify the flux and repeat the exchange. For Klingons the exchange caused a momentary feeling of dizziness, similar to the side effects of a concussion.

The different quantum states of alternate quantum realities could be scanned through a broken quantum fissure using a subspace differential pulse. An energy surge within the subspace differential pulse would destabilize a fissure. A destabilized fissure led to an exponentially increasing destruction of the barriers between different quantum realities, causing quantum incursions within the sector of the anomaly. Eventually emerging all intersected quantum realities to the one that initiated the pulse. Remodulated warp engines could be used to emit a broad spectrum inverse warp field from the ship that originally weakened the barriers to seal the anomaly and send everything back to their indigenous realities. Due to the uncertainty principle, the ship and its occupants sealing the fissure would emerge back into their own reality several days before or after the event. (TNG: "Parallels")