Quantum jump

For other uses, seeQuantum jump (disambiguation).

Aquantum jumpis the abrupttransitionof a quantum system (atom,molecule,atomic nucleus) from onequantum stateto another, from oneenergy levelto another. When the system absorbs energy, there is a transition to a higher energy level (excitation); when the system loses energy, there is a transition to a lower energy level.

The concept was introduced byNiels Bohr,in his 1913Bohr model.

A quantum jump is a phenomenon that is peculiar to quantum systems and distinguishes them from classical systems, where any transitions are performed gradually. In quantum mechanics, such jumps are associated with the non-unitary evolution of a quantum-mechanical system during measurement.

A quantum jump can be accompanied by the emission or absorption ofphotons;energy transfer during a quantum jump can also occur by non-radiative resonant energy transfer or in collisions with other particles.

In modern physics, the concept of a quantum jump is rarely used; as a rule scientists speak of transitions between quantum states or energy levels.

Atomic electron transition

Main article:Atomic electron transition

Grotrian diagram of a quantum 3-level system with characteristic transition frequencies,$\ Omega$₁₂and$\ Omega$₁₃,and excited state lifetimes$\Gamma$₂and$\Gamma$₃

Atomic electron transitions cause the emission or absorption ofphotons.Their statistics arePoissonian,and the time between jumps isexponentially distributed.The damping time constant (which ranges fromnanosecondsto a few seconds) relates to the natural, pressure, and fieldbroadening of spectral lines.The larger the energy separation of the states between which the electron jumps, the shorter thewavelengthof the photon emitted.

EMCCD camera and photomultiplier tube signals while driving quantum jumps on the 674 nm transition of⁸⁸Sr⁺

In anion trap,quantum jumps can be directly observed by addressing a trapped ion with radiation at two different frequencies to drive electron transitions.This requires one strong and one weak transition to be excited (denoted$\ Omega$₁₂and$\ Omega$₁₃respectively in the figure to the right). The electron energy level,$|2\rangle$,has a short lifetime,$\Gamma$₂which allows for constant emission of photons at a frequency$\ Omega$₁₂which can be collected by a camera and/orphotomultiplier tube.State$|3\rangle$has a relatively long lifetime$\Gamma$₃which causes an interruption of the photon emission as the electron gets shelved in state through application of light with frequency$\ Omega$_13.The ion going dark is a direct observation of quantum jumps.

Molecular electronic transition

Main article:Molecular electronic transition

Sources

• Are there quantum jumps?
• «There are no quantum jumps, nor are there particles!» by H. D. Zeh,Physics LettersA172,189 (1993).
• Gleick, James Gleick (October 21, 1986)."Physicists Finally Get To See the Quantum Jump".New York Times.New York City.Retrieved2013-08-23.
• Der Quantensprung im Bohrschen AtommodellFrühe Quantenphysik
• Der QuantensprungDie zweifelhafte Karriere eines Fachausdrucks (ZEIT 1996)
• M.B. Plenio und P.L. KnightThe Quantum Jump Approach to Dissipative Dynamics in Quantum Optics,vgl. auch Rev. Mod. Phys.70101–144 (1998). (Beschreibung der Dynamik offener Systeme mittels Quantensprüngen)
• Historisches zum Quantensprung,Sommerfeld und Einstein 1911