ObjectiveCellular temperature imaging can assist scientists in studying and comprehending the temperature distribution within cells, revealing critical information about cellular metabolism and biochemical processes. Currently, cell temperature imaging techniques based on fluorescent temperature probes suffer from limitations such as low temperature resolution and a limited measurement range. This paper aims to develop a single-cell temperature imaging and real-time monitoring technique by leveraging the temperature-dependent properties of single-molecule quantum coherence processes.MethodsUsing femtosecond pulse lasers, we prepare delayed and phase-adjustable pairs of femtosecond pulses. These modulated pulse pairs excite fluorescent single molecules labeled within cells through a microscopic system, followed by the collection and recording of the arrival time of each fluorescent photon. By defining the quantum coherence visibility (V) of single molecules in relation to the surrounding environmental temperature, a correspondence between V and environmental temperature is established. By modulating and demodulating the arrival times of fluorescent photons, we obtain the local temperature of single molecules. Combined with scanning imaging, we finally achieve temperature imaging and real-time detection of cells.ResultsThis method achieves high precision (temperature resolution <0.1°C) and a wide temperature range (10-50°C) for temperature imaging and measurement, and it enables the observation of temperature changes related to individual cell metabolism.ConclusionThis research contributes to a deeper understanding of cellular metabolism, protein function, and disease mechanisms, providing a valuable tool for biomedical research.
ObjectiveCellular temperature imaging can assist scientists in studying and comprehending the temperature distribution within cells, revealing critical information about cellular metabolism and biochemical processes. Currently, cell temperature imaging techniques based on fluorescent temperature probes suffer from limitations such as low temperature resolution and a limited measurement range. This paper aims to develop a single-cell temperature imaging and real-time monitoring technique by leveraging the temperature-dependent properties of single-molecule quantum coherence processes.MethodsUsing femtosecond pulse lasers, we prepare delayed and phase-adjustable pairs of femtosecond pulses. These modulated pulse pairs excite fluorescent single molecules labeled within cells through a microscopic system, followed by the collection and recording of the arrival time of each fluorescent photon. By defining the quantum coherence visibility (V) of single molecules in relation to the surrounding environmental temperature, a correspondence between V and environmental temperature is established. By modulating and demodulating the arrival times of fluorescent photons, we obtain the local temperature of single molecules. Combined with scanning imaging, we finally achieve temperature imaging and real-time detection of cells.ResultsThis method achieves high precision (temperature resolution <0.1°C) and a wide temperature range (10-50°C) for temperature imaging and measurement, and it enables the observation of temperature changes related to individual cell metabolism.ConclusionThis research contributes to a deeper understanding of cellular metabolism, protein function, and disease mechanisms, providing a valuable tool for biomedical research.
In fluorescence imaging and detection, undesired fluorescence interference (such as autofluorescence) often hampers the contrast of the image and even prevents the identification of structures of interest. Here, we develop a quantum coherent modulation-enhanced (QCME) single-molecule imaging microscopy (SMIM) to substantially eliminate the strong fluorescence interference, based on manipulation of the excited-state population probability of a single molecule. By periodically modulating the phase difference between the ultrashort pulse pairs and performing a discrete Fourier transform of the arrival time of emitted photons, the decimation of single molecules from strong interference in QCME-SMIM has been clearly determined, where the signal-to-interference ratio is enhanced by more than 2 orders of magnitude. This technique, confirmed to be universal to organic dyes and linked with biomacromolecules, paves the way to high-contrast bioimaging under unfavorable conditions.
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.
Live-cell imaging of cellular and tissue samples relies predominantly on optical modalities, such as fluorescence, confocal, and multiphoton microscopy, in which cellular information is encoded in emitted photons. Photons scatter and attenuate in biological samples, restricting depth resolution, while the excitation light required to produce them induces photodamage that perturbs the very biology under observation. Magnetic fields, by contrast, traverse biological samples without attenuation at cellular length scales, but the imaging modality that extracts the encoded information, magnetic resonance imaging, cannot resolve individual cells. Here we present Quantum Cell Monitoring (QCM), a widefield nitrogen-vacancy magnetometry platform that encodes single-cell information in stray magnetic fields rather than emitted photons and reads it out at subcellular resolution. Integrated with a specialized live-cell incubator, QCM tracks magnetically labeled living cancer for up to 72 h through their individual magnetic field signatures. It captures single-cell mitosis and morphological remodeling, as well as cell cluster formation, splitting, and migration even within dense regions where brightfield contrast collapses. By shifting the carrier of single-cell information from propagating optical photons to static magnetic stray fields, QCM decouples cell from cellular optical accessibility and auto-fluorescence, enabling sustained live-cell observation in regimes inaccessible to optical microscopy.
• Overcoming existing limitations of ultra-low temperatures and silicon bases by utilizing 3-nanometer (nm) fluorescent proteins as qubits. • Successful control of quantum states (Rabi oscillations) within E. coli at room temperature and human cells. • Enabling ultra-precise measurement of magnetic fields and temperatures inside cells... Heralding a paradigm shift in new drug development and cell imaging technologies. [Quantum Biology Society] The long-standing conventional wisdom that quantum technology can only be realized at cryogenic temperatures based on hard, highly ordered materials like diamonds or silicon has been broken. Biological quantum bits (qubits) that operate directly inside the watery and complex biological environment—that is, inside 'living cells'—have been developed for the first time in the world. Citing a study recently published in the international academic journal Nature, the US-based Science News reported that scientists have created biological qubits merely 3 nanometers (nm) in diameter using fluorescent proteins. ■ Controlling Quantum Mechanics with Biotechnology Tools Existing quantum technologies require extremely cold temperatures and strictly controlled environments, making them difficult to apply to unstable settings like the inside of living organisms. However, the research team chose to manipulate the spin of the 'fluorophore,' a specific part of a protein that emits light when exposed to it. Using genetic engineering, the research team directly produced this protein inside laboratory cells. They then succeeded in awakening the quantum properties of the protein by shooting laser light at it, fine-tuning it with microwaves, and observing the luminescence phenomenon. ■ Qubits Operating at 'Room Temperature'... Reading the Microenvironment of Diseases The most surprising achievement is the temperature of the experimental environment. Unlike the majority of qubits that lose their function at high temperatures, this biological qubit successfully demonstrated quantum state changes called 'Rabi oscillations' inside human cells at 175 Kelvin (-98.15°C), as well as inside E. coli at room temperature. This technological leap signifies the birth of 'biological quantum sensors' that can measure microscopic conditions such as magnetic fields and temperatures inside cells with unprecedented precision. It is expected to enable a new dimension of medical imaging technology and targeting by allowing the root causes of diseases to be identified at the intracellular molecular level. Amidst recent active academic movements in South Korea to integrate quantum mechanics into life phenomena, centered around the Quantum Biology Society, this study is also providing great inspiration for R&D strategies in the pharmaceutical and biotech industries. In particular, such quantum sensing technology, which can precisely target and measure the microenvironment inside cells, could become a powerful key to maximizing the value of innovative pipelines in the future. Fluorescent proteins, which have been used for decades in biology labs to track proteins and cancer cells, are now wearing the clothes of quantum mechanics and opening a new era of quantum biology.
Recovering both amplitude and phase information from a system is a fundamental goal of optical imaging. At the same time, it is crucial to operate at low photon doses to avoid altering the sample, particularly in biological applications. Quantum imaging provides a powerful route to extract more information per photon than classical techniques, which are ultimately limited by shot-noise. However, the trade-off between quantum noise reduction and spatial resolution has long been regarded as a major obstacle to the application of quantum techniques to small cellular and sub-cellular structures, where they could offer the greatest benefits. Here, we overcome this limitation by demonstrating sub-shot-noise quantitative phase imaging of biological cells based on the transport-of-intensity equation, enabling high-fidelity, label-free imaging of key cellular and sub-cellular features. We achieve high-resolution phase imaging limited only by the numerical aperture, while simultaneously obtaining a resolution-independent quantum advantage. Unlike other quantum imaging approaches, our method operates in a quasi-single-shot, wide-field configuration, retrieves both phase and amplitude information, and does not rely on interferometric measurements, making it intrinsically fast and stable. These results pave the way for the immediate application of sub-shot-noise imaging in biological microscopy.
Two revolutions in quantum sensing are converging on the same microscope stage. Biological qubits have emerged as genetically encoded, optically addressable quantum systems inside live cells. Solid state spin based qubits have been entangled and used as nanoscale correlator magnetometers, delivering sensitivity and spatial-resolution gains that single-spin probes cannot reach. Here we report a pulsed quantum microscope that enables simultaneous quantum state manipulation of both qubit technologies in live cells. The platform combines nanosecond-gated optical excitation at 450 nm and 520 nm, three-dimensional diffraction-limited addressing by galvo beam scanning and piezo objective focus, rapidly switched static and radio-frequency magnetic fields, single-photon timing with picosecond resolution, and microwave control for frequencies from DC to 5 GHz, including the 2.87 GHz resonance of solid state spins, the 500 MHz to 800 MHz resonance of radical pairs in biological qubits, and any future qubit resonance in the GHz range. Live cell imaging with simultaneous biological and solid state nanoparticle qubits in the same cell demonstrates the power of this technique for multiplexed quantum sensing. We anticipate this approach will open new opportunities for researchers to explore quantum sensing in live cells, and, ultimately, entanglement between a solid-state qubit and a protein-hosted spin qubit.