Abstract
We use laser light and a transmission electron microscope to modulate a free-electron beam into high-contrast electron pulses and free-electron qubits by using temporal Talbot revivals. At large enough propagation distances, the discrete energy sidebands from a laser modulation acquire special phases and group delays that optimize or cancel their time-domain interference, producing a revival or alternatively a pulse train at close to 100% modulation depth. A sequence of two laser interactions at an optimized propagation distance allows us to coherently control adjacent energy sidebands in amplitude and phase in the way of a qubit. The use of continuous-wave laser light provides these modulations at almost the full brightness of the beam source. Free electrons under large-distance laser control are therefore a promising tool for ultrafast material characterizations or investigations of free-electron quantum mechanics.
Highlights
The electron microscope is one of the most versatile instruments for investigating the atomic structure of complex materials, but it is useful for understanding the quantum mechanics of the free electron and its strong interactions with coherent and incoherent light [1,2,3,4,5,6]
For characterizations of ultrafast material dynamics, electrons can be modulated in time by the cycles of laser light [7,8,9,10], providing femtosecond and attosecond time resolution for applications in photon-induced electron microscopy [11,12], ultrafast electron diffraction [9], or waveform electron microscopy [13,14]
According to the analytical predictions, 120 keV corresponds to generating electron pulses with shortest duration [10], whereas 75 keV should roughly correspond to a half-revival distance between the two interactions
Summary
The electron microscope is one of the most versatile instruments for investigating the atomic structure of complex materials, but it is useful for understanding the quantum mechanics of the free electron and its strong interactions with coherent and incoherent light [1,2,3,4,5,6]. Short electron pulses; these pulses lengthen to half the inverse modulation frequency at the benefit of zero temporal background; the wave packet turns again into the same ultrashort pulses as before; and the wave function experiences an almost full restoration to the original state after the initial laser modulation. This chain of transformations and revivals recurs multiple times upon further propagation [23] and is robust against decoherence or dispersion. A second laser interaction at a properly chosen fractional revival time allows us to demonstrate experimental evidence for the production of a free-electron qubit
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