Lightwave Quantum Spectroscopy

Understanding and Controlling the Quantum World of Electrons: Lightwaves spanning the visible to mid-infrared spectrum of laser pulses are able to access the quantum world of electrons. By manipulating electrons at the quantum level, we can harness phenomena like coherence, entanglement, and quantum interference to create ultra-efficient electronic devices, quantum processors, and next-generation materials with tailored properties. Understanding and controlling quantum dynamics can lead to advances in energy-efficient electronics, secure communication, and novel approaches to information processing that push the boundaries of what is technologically possible.

More preciscely, ultrafast coherent control may allow us to probe the electron wavefunction in solids, specifically its phase. To achieve this, we will develop advanced interferometric techniques, including lightwave-controlled Bloch electron interferometry and sub-cycle-resolved pump-probe spectroscopy. By accessing the coherence of the electron wavefunction, we can study how long electrons remain coherent during dynamic processes and how intra- and interband quantum phases influence electronic excitation and transport.

The wavefunction encodes an electron's crystal momentum and energy, providing a direct map of the material’s band structure. It includes details on band gaps, carrier dynamics, and topological properties, such as surface states in topological insulators. Its phase also reveals the Berry curvature, enabling insights into quantum effects like the anomalous Hall effect, Chern numbers, and field-driven topological transitions.

Access to the wave function also reveals coherence properties that shed light on phase conservation in scattering and decoherence mechanisms in quantum materials. This enables real-time observation of coherence lifetimes, electron-phonon coupling, and many-body interactions that affect conductivity, superconductivity, and other material properties. On the sub-cycle timescale, the wavefunction also captures phenomena like band tunneling, Floquet state dynamics, and attosecond electron responses.

These insights provide a unique window into nonequilibrium phenomena, enabling control over topological switching and ultrafast quantum phase transitions while advancing our understanding of fundamental quantum principles. Measuring the temporal evolution of the wave function could offer unprecedented insight and control over electronic, optical, and quantum properties akin to a petahertz-fast oscilloscope for the quantum world of electrons.