Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1012.2366 · Nature Physics

Femtosecond coherence and quantum control of single molecules at room temperature

Richard Hildner, Daan Brinks, N.F. van Hulst

Published Dec 12, 2010• 164 citations
arXivHTMLPDF
DOI
10.1038/nphys1858

Related papers

Coherent Control of Single Molecules at Room Temp

N.F. van Hulst, Daan Brinks, Richard Hildner

Bulletin of the American Physical Society•Mar 22, 2011•0 citations

Quantum Control of Atoms and Small Molecules with Intense Femtosecond Pulses

Adi Natan, Yaron R. Silberberg

•Jan 1, 2009•0 citations

Rapid and robust control of single quantum dots

Nicolò Accanto, Pablo M. de Roque, Marcial Galvan-Sosa +3 more

The combination of single particle detection and ultrafast laser pulses is an instrumental method to track dynamics at the femtosecond time scale in single molecules, quantum dots and plasmonic nanoparticles. Optimal control of the extremely short-lived coherences of these individual systems has so far remained elusive, yet its successful implementation would enable arbitrary external manipulation of otherwise inaccessible nanoscale dynamics. In ensemble measurements, such control is often achieved by resorting to a closed-loop optimization strategy, where the spectral phase of a broadband laser field is iteratively optimized. This scheme needs long measurement times and strong signals to converge to the optimal solution. This requirement is in conflict with the nature of single emitters whose signals are weak and unstable. Here we demonstrate an effective closed-loop optimization strategy capable of addressing single quantum dots at room temperature, using as feedback observable the two-photon photoluminescence induced by a phase-controlled broadband femtosecond laser. Crucial to the optimization loop is the use of a deterministic and robust-against-noise search algorithm converging to the theoretically predicted solution in a reduced amount of steps, even when operating at the few-photon level. Full optimization of the single dot luminescence is obtained within ~100 trials, with a typical integration time of 100 ms per trial. These times are faster than the typical photobleaching times in single molecules at room temperature. Our results show the suitability of the novel approach to perform closed-loop optimizations on single molecules, thus extending the available experimental toolbox to the active control of nanoscale coherences. Femtosecond laser control allows to harness short-lived coherences and study molecular ultrafast dynamics. Translating such coherent-control schemes from the ensemble to single molecules is challenging due to signal fluctuation and photo-dissociation. Now, Nicolò Accanto and Pablo de Roque from ICFO - the Institute of Photonic Sciences in Barcelona, and colleagues, have reduced the time needed to perform closed-loop optimisations. By employing a new simple deterministic algorithm, and assuming simple optimisation landscapes, they accomplished a phase-only optimisation of the two-photon photoluminescence of a single quantum dot. Combining this rapid feedback process within the search algorithm with a sensitive microscopy technique, they were able to optimise on signals even at the few-photon level, enabling the coherent control of individual quantum-dots at room temperature in a matter of seconds - a speedup critical for capturing details of biomolecular interactions, for instance.

Light Science & Applications•Sep 28, 2016•23 citations

Nanoscale Coherent Control. Ultrafast dynamics of single molecules, individual light harvesting complexes and discrete nanoantennas at room temperature.

Daan Brinks

Ultrafast pulses allow observation of molecular dynamics with femtosecond time resolution through pump probe experiments. However, averaging over an ensemble of molecules tends to wash out phase sensitive information, necessary to probe quantum effects, due to the intrinsic inhomogeneity in molecular conformations, orientations and interactions that lead to unique potential energy landscapes for each molecule. It is therefore important to go beyond the ensemble average when looking at quantum dynamics of organic systems at room temperature, and resolve the behaviour of specific molecules on an individual basis. In this thesis, we show the creation, manipulation and observation of ultrafast coherent effects in single molecules at room temperature, and resolve a certain measure of environmental influence on the specific dynamics of each molecule. Moreover, we apply this insight to investigate a functional light harvesting biosystem, and lay the basis for a technique that has the time and space resolution required to observe these systems in vivo. In chapter 1, we introduce the concepts and techniques the research in this thesis is built on. In chapter 2, we treat the possibility of controlling ultrafast pulses at the high-NA diffraction limit, and come to conclusions about the procedure to follow there that hold for all pulse-shaping experiments. We show in proof of principle experiments that we can control the ultrafast characteristics of optical pulses in nanometric excitation volumes. In chapters 3 and 4 we report the creation, detection and control of ultrafast quantum dynamics in single organic molecules at room temperature. We show that manipulation of superposition states is possible in these systems within a coherence dephasing time of ~50 fs. This leads to the first observation of rabi-oscillations in room temperature single molecules, to ultrafast operation of an organic qubit, and to the creation of non-stationary superposition states (vibrational wavepackets). We probe the influence of the local environment on the composition and dynamics of these wavepackets and show we can optimize the state preparation protocol for each individual molecule in its own nanoenvironment, leading to high fidelity coherent control. In these chapters we lay out the proof of principle work of detecting the quantumdynamics of a complex system in interaction with its environment at room temperature. In chapter 5 we discuss application of these techniques to the investigation of long lived coherence in photosynthetic systems. We show that electronic coherence between different rings of the LH2 system persists to time scales of 100s of femtoseconds at room temperature. Moreover we show that the energy transfer pathways in LH2 adapt to environmentally induced changes in the molecule and that the nature of the transfer remains coherent for each pathway, providing strong evidence that coherent energy transfer is the optimum process for energy transfer in photosynthesis. Finally, in chapter 6 we take the technical development one step further and report on the creation of a framework based on plasmonic antennas that allows for control of the amplitude-phase characteristics in nanometric sized hotspot fields. We show for the first time that the ultrafast characteristics of plasmonic hotspots can directly be engineered through design of the plasmonic system and experimentally demonstrate two much-anticipated examples: a sub-diffraction resolution phase shaper and an ultrafast plasmonic switch for pump probe experiments. The results presented in this thesis form the first creation and observation of ultrafast coherent dynamics in individual molecular systems at room temperature. This is a necessary step to be able to do true quantum tomography in complex systems, resolve the influence of the environment on molecular dynamics, and investigate the physics that determines evolutionary optimization and functionality in biomolecules.

•Oct 19, 2012•0 citations

Coherent Control of Single Molecules via Phase-Shaped Two-Photon Excitation at Room Temperature

X. X. Xu, Tobias M. Herkenrath, Ullrich Scherf +1 more

Coherent control has been achieved in atoms and small molecules in gas phase during the past few decades. An intriguing demonstration of coherent control is a so-called “dark pulse” that cancels 2-photon transition probabilities despite exposing the target to the full power spectrum of transform-limited laser pulses. However, for larger functional molecules in condensed phase at room temperature, ensemble measurements do typically not allow exerting full control over competing pathways due to the unavoidable influence of the surrounding (mostly complex) environment. Here, we demonstrate room-temperature coherent control exploiting a nonresonant 2-photon transition into a higher excited state of single conjugated polymer chains embedded in a disordered matrix, including proof-of-principle experiments on bulk films. To manipulate the 2-photon transition probability, we exploit complex pulse sequences, created by a systematically varied cosinusoidal spectral phase applied to the excitation laser spectrum. For single molecules, the phase-dependent response varies from molecule to molecule, which reflects the spectral heterogeneity (position, linewidth) of their 2-photon transitions. These data indicate that coherent control of single molecules requires optimization of parameters for each individual molecule. The experimental data are reproduced by a simple model that allows to directly retrieve the 2-photon absorption spectrum of each single molecule. Our coherent-control approach is a powerful and robust way to obtain spectral characteristics of higher excited states of single molecules and to manipulate the excited-state dynamics in condensed phase at room temperature. It holds the potential to be useful for the characterization of complex organic functional materials.

Ultrafast Science•Jan 1, 2025•3 citations

Room temperature quantum coherence in a potential molecular qubit

Katharina Bader, Dominik Dengler, Samuel Lenz +4 more

Nature Communications•Oct 20, 2014•389 citations
The combination of single particle detection and ultrafast laser pulses is an instrumental method to track dynamics at the femtosecond time scale in single molecules, quantum dots and plasmonic nanoparticles. Optimal control of the extremely short-lived coherences of these individual systems has so far remained elusive, yet its successful implementation would enable arbitrary external manipulation of otherwise inaccessible nanoscale dynamics. In ensemble measurements, such control is often achieved by resorting to a closed-loop optimization strategy, where the spectral phase of a broadband laser field is iteratively optimized. This scheme needs long measurement times and strong signals to converge to the optimal solution. This requirement is in conflict with the nature of single emitters whose signals are weak and unstable. Here we demonstrate an effective closed-loop optimization strategy capable of addressing single quantum dots at room temperature, using as feedback observable the two-photon photoluminescence induced by a phase-controlled broadband femtosecond laser. Crucial to the optimization loop is the use of a deterministic and robust-against-noise search algorithm converging to the theoretically predicted solution in a reduced amount of steps, even when operating at the few-photon level. Full optimization of the single dot luminescence is obtained within ~100 trials, with a typical integration time of 100 ms per trial. These times are faster than the typical photobleaching times in single molecules at room temperature. Our results show the suitability of the novel approach to perform closed-loop optimizations on single molecules, thus extending the available experimental toolbox to the active control of nanoscale coherences. Femtosecond laser control allows to harness short-lived coherences and study molecular ultrafast dynamics. Translating such coherent-control schemes from the ensemble to single molecules is challenging due to signal fluctuation and photo-dissociation. Now, Nicolò Accanto and Pablo de Roque from ICFO - the Institute of Photonic Sciences in Barcelona, and colleagues, have reduced the time needed to perform closed-loop optimisations. By employing a new simple deterministic algorithm, and assuming simple optimisation landscapes, they accomplished a phase-only optimisation of the two-photon photoluminescence of a single quantum dot. Combining this rapid feedback process within the search algorithm with a sensitive microscopy technique, they were able to optimise on signals even at the few-photon level, enabling the coherent control of individual quantum-dots at room temperature in a matter of seconds - a speedup critical for capturing details of biomolecular interactions, for instance.
Ultrafast pulses allow observation of molecular dynamics with femtosecond time resolution through pump probe experiments. However, averaging over an ensemble of molecules tends to wash out phase sensitive information, necessary to probe quantum effects, due to the intrinsic inhomogeneity in molecular conformations, orientations and interactions that lead to unique potential energy landscapes for each molecule. It is therefore important to go beyond the ensemble average when looking at quantum dynamics of organic systems at room temperature, and resolve the behaviour of specific molecules on an individual basis. In this thesis, we show the creation, manipulation and observation of ultrafast coherent effects in single molecules at room temperature, and resolve a certain measure of environmental influence on the specific dynamics of each molecule. Moreover, we apply this insight to investigate a functional light harvesting biosystem, and lay the basis for a technique that has the time and space resolution required to observe these systems in vivo. In chapter 1, we introduce the concepts and techniques the research in this thesis is built on. In chapter 2, we treat the possibility of controlling ultrafast pulses at the high-NA diffraction limit, and come to conclusions about the procedure to follow there that hold for all pulse-shaping experiments. We show in proof of principle experiments that we can control the ultrafast characteristics of optical pulses in nanometric excitation volumes. In chapters 3 and 4 we report the creation, detection and control of ultrafast quantum dynamics in single organic molecules at room temperature. We show that manipulation of superposition states is possible in these systems within a coherence dephasing time of ~50 fs. This leads to the first observation of rabi-oscillations in room temperature single molecules, to ultrafast operation of an organic qubit, and to the creation of non-stationary superposition states (vibrational wavepackets). We probe the influence of the local environment on the composition and dynamics of these wavepackets and show we can optimize the state preparation protocol for each individual molecule in its own nanoenvironment, leading to high fidelity coherent control. In these chapters we lay out the proof of principle work of detecting the quantumdynamics of a complex system in interaction with its environment at room temperature. In chapter 5 we discuss application of these techniques to the investigation of long lived coherence in photosynthetic systems. We show that electronic coherence between different rings of the LH2 system persists to time scales of 100s of femtoseconds at room temperature. Moreover we show that the energy transfer pathways in LH2 adapt to environmentally induced changes in the molecule and that the nature of the transfer remains coherent for each pathway, providing strong evidence that coherent energy transfer is the optimum process for energy transfer in photosynthesis. Finally, in chapter 6 we take the technical development one step further and report on the creation of a framework based on plasmonic antennas that allows for control of the amplitude-phase characteristics in nanometric sized hotspot fields. We show for the first time that the ultrafast characteristics of plasmonic hotspots can directly be engineered through design of the plasmonic system and experimentally demonstrate two much-anticipated examples: a sub-diffraction resolution phase shaper and an ultrafast plasmonic switch for pump probe experiments. The results presented in this thesis form the first creation and observation of ultrafast coherent dynamics in individual molecular systems at room temperature. This is a necessary step to be able to do true quantum tomography in complex systems, resolve the influence of the environment on molecular dynamics, and investigate the physics that determines evolutionary optimization and functionality in biomolecules.
Coherent control has been achieved in atoms and small molecules in gas phase during the past few decades. An intriguing demonstration of coherent control is a so-called “dark pulse” that cancels 2-photon transition probabilities despite exposing the target to the full power spectrum of transform-limited laser pulses. However, for larger functional molecules in condensed phase at room temperature, ensemble measurements do typically not allow exerting full control over competing pathways due to the unavoidable influence of the surrounding (mostly complex) environment. Here, we demonstrate room-temperature coherent control exploiting a nonresonant 2-photon transition into a higher excited state of single conjugated polymer chains embedded in a disordered matrix, including proof-of-principle experiments on bulk films. To manipulate the 2-photon transition probability, we exploit complex pulse sequences, created by a systematically varied cosinusoidal spectral phase applied to the excitation laser spectrum. For single molecules, the phase-dependent response varies from molecule to molecule, which reflects the spectral heterogeneity (position, linewidth) of their 2-photon transitions. These data indicate that coherent control of single molecules requires optimization of parameters for each individual molecule. The experimental data are reproduced by a simple model that allows to directly retrieve the 2-photon absorption spectrum of each single molecule. Our coherent-control approach is a powerful and robust way to obtain spectral characteristics of higher excited states of single molecules and to manipulate the excited-state dynamics in condensed phase at room temperature. It holds the potential to be useful for the characterization of complex organic functional materials.