Kai Sheng Lee, Yuanzheng Paul Tan, L H Nguyen, Rangga P. Budoyo, K H Park, Christoph Hufnagel, Yung Szen Yap, Nadja Møbjerg, Vlatko Vedral, Tomasz Paterek, Rainer Dumke
Abstract Quantum and biological systems are seldom discussed together as they seemingly demand opposing conditions. Life is complex, ‘hot and wet’ whereas quantum objects are small, cold and well controlled. Here, we overcome this barrier with a tardigrade—a microscopic multicellular organism known to tolerate extreme physicochemical conditions via a latent state of life known as cryptobiosis. We observe coupling between the animal in cryptobiosis and a superconducting quantum bit and prepare a highly entangled state between this combined system and another qubit. The tomographic data shows entanglement in the qubit-qubit-tardigrade system, with the tardigrade modelled as an ensemble of harmonic oscillators or collection of electric dipoles. The animal is then observed to return to its active form after 420 h at sub 10 mK temperatures and pressures below 6 × 10 − 6 mbar, setting a new record for the conditions that a complex form of life can survive.
Abstract Quantum and biological systems are seldom discussed together as they seemingly demand opposing conditions. Life is complex, ‘hot and wet’ whereas quantum objects are small, cold and well controlled. Here, we overcome this barrier with a tardigrade—a microscopic multicellular organism known to tolerate extreme physicochemical conditions via a latent state of life known as cryptobiosis. We observe coupling between the animal in cryptobiosis and a superconducting quantum bit and prepare a highly entangled state between this combined system and another qubit. The tomographic data shows entanglement in the qubit-qubit-tardigrade system, with the tardigrade modelled as an ensemble of harmonic oscillators or collection of electric dipoles. The animal is then observed to return to its active form after 420 h at sub 10 mK temperatures and pressures below 6 × 10 − 6 mbar, setting a new record for the conditions that a complex form of life can survive.
• A study published on arXiv conducted an unprecedented experiment by inducing a highly resilient multicellular organism, a tardigrade, into a state of suspended animation (cryptobiosis) and placing it directly on a superconducting qubit circuit in an extreme vacuum at millikelvin (mK) temperatures. • The researchers claim that quantum entanglement was formed between the tardigrade and the qubit system, evidenced by changes in the resonance frequency and coupling with a second qubit. • The study confirmed that the tardigrade miraculously revived to an active state upon returning to room temperature and atmospheric pressure after exposure to extreme quantum experimental conditions (sub 10 mK, 6×10^{-6} mbar), pioneering the exploration of the extreme limits where a multicellular organism can survive while integrated with quantum hardware. [Quantum Biology Society] While quantum systems generally require cold, controlled environments, living organisms exist in hot, wet conditions, leading to the assumption that the two systems are inherently incompatible. However, an unconventional attempt to directly couple a multicellular organism with quantum hardware has been reported in the academic community, sparking fierce debate and opening new frontiers in quantum biology. The paper, titled "Entanglement between superconducting qubits and a tardigrade," released on the preprint repository arXiv, details the results of experimentally modeling the interaction and quantum entanglement formation between a highly resilient tardigrade and superconducting qubits. A multinational research team, including K. S. Lee and R. Dumke from Nanyang Technological University and N. Møbjerg from the University of Copenhagen, led this experiment. ■ Extreme Integration of a Living Organism and Quantum Hardware The research team desiccated an adult tardigrade (R. varicornatus) collected in Denmark to induce a state of cryptobiosis (the "tun" state) and placed it between the capacitor plates of a superconducting transmon qubit (Qubit B). The system was then cooled to sub-10 millikelvin (mK) temperatures and an extreme vacuum of 6×10^{-6} mbar. In this state, the tardigrade is placed in perfect stasis, essentially suspending all chemical metabolic processes. ■ Evidence of Quantum Entanglement: Resonance Frequency Shift and State Tomography The maximum resonance frequency of Qubit B, where the tardigrade was placed, shifted down by 8 MHz, which the researchers interpreted as an interaction driven by the tardigrade's dielectric properties. Furthermore, the researchers conducted an experiment to entangle this Qubit B-tardigrade coupled system with a second qubit (Qubit A). After reconstructing the system's density matrix via quantum state tomography, it showed a high fidelity of 82% with the expected entangled state. Based on this data, the team claimed that the tardigrade was in a state of quantum entanglement with the other qubits within the tripartite system (Qubit A - Qubit B - Tardigrade). ■ Miraculous Revival After Extreme Exposure Most surprisingly, even after prolonged exposure to these extreme quantum experimental conditions, the tardigrade miraculously revived to an active metabolic state in liquid water upon returning to atmospheric pressure and room temperature. According to the paper, the tardigrade remained at sub 10 mK temperatures for 420 hours. This sets a new record for the extreme conditions under which a complex multicellular organism can survive, demonstrating that the cryptobiotic state perfectly suspends the organism's chemical activity enough to withstand quantum experiments. ■ New Debates and Possibilities in Quantum Biology This study has sparked an intense debate within the physics community over whether a living organism can truly be entangled with a quantum system. Some scholars strongly object, arguing that the tardigrade merely acted as a dielectric material passively influencing the electric field of the qubit circuit rather than directly participating in entanglement, making it difficult to view this as true biological quantum entanglement. Nevertheless, this experiment is a pioneering case demonstrating that an entire living organism can be physically coupled to quantum hardware and subsequently maintain its biological functions. It is evaluated as having empirically surpassed the concept of complementarity in living organisms proposed by Niels Bohr. It undeniably presents an exciting new path toward developing hybrid systems composed of living matter and quantum bits in the future.
Recent advances in the spectroscopy of biomolecules have highlighted the possibility of quantum coherence playing an active role in biological energy transport. The revelation that quantum coherence can survive in the hot and wet environment of biology has generated a lively debate across both the physics and biology communities. In particular, it remains unclear to what extent non-trivial quantum effects are used in biology and what advantage, if any, they afford. We propose an analogue quantum simulator, based on currently available techniques in ultra-cold atom physics, to study a model of energy and electron transport based on the Holstein Hamiltonian. By simulating the salient aspects of a biological system in a tunable laboratory set-up, we hope to gain insight into the validity of several theoretical models of biological quantum transport in a variety of relevant parameter regimes.
The most striking feature of quantum mechanics is the existence of superposition states, where an object appears to be in different situations at the same time. The existence of such states has been previously tested with small objects, such as atoms, ions, electrons and photons (Zoller et al 2005 Eur. Phys. J. D 36 203–28), and even with molecules (Arndt et al 1999 Nature 401 680–2). More recently, it has been shown that it is possible to create superpositions of collections of photons (Deléglise et al 2008 Nature 455 510–14), atoms (Hammerer et al 2008 arXiv:0807.3358) or Cooper pairs (Friedman et al 2000 Nature 406 43–6). Very recent progress in optomechanical systems may soon allow us to create superpositions of even larger objects, such as micro-sized mirrors or cantilevers (Marshall et al 2003 Phys. Rev. Lett. 91 130401; Kippenberg and Vahala 2008 Science 321 1172–6; Marquardt and Girvin 2009 Physics 2 40; Favero and Karrai 2009 Nature Photon. 3 201–5), and thus to test quantum mechanical phenomena at larger scales. Here we propose a method to cool down and create quantum superpositions of the motion of sub-wavelength, arbitrarily shaped dielectric objects trapped inside a high-finesse cavity at a very low pressure. Our method is ideally suited for the smallest living organisms, such as viruses, which survive under low-vacuum pressures (Rothschild and Mancinelli 2001 Nature 406 1092–101) and optically behave as dielectric objects (Ashkin and Dziedzic 1987 Science 235 1517–20). This opens up the possibility of testing the quantum nature of living organisms by creating quantum superposition states in very much the same spirit as the original Schrödinger's cat 'gedanken' paradigm (Schrödinger 1935 Naturwissenschaften 23 807–12, 823–8, 844–9). We anticipate that our paper will be a starting point for experimentally addressing fundamental questions, such as the role of life and consciousness in quantum mechanics.
• Published on bioRxiv, successfully observed multiple-quantum coherence (MQC) and SU(1,1) pair dynamics in proton spin ensembles of the living human brain. • Mathematically proved that the observed signal is not a classical SU(2) exchange model, but a non-compact SU(1,1) symmetry squeezing phenomenon based on double-quantum (DQ) coherence. • Overcame the thermodynamic obstruction of high-temperature biological environments at body temperature and presented a framework that strongly supports the possible existence of macroscopic many-body entanglement inside the brain. [Quantum Biology Society] The hypothesis that the living human brain could fundamentally operate like a giant quantum computer has long been a hot potato in the scientific community. This is because conventional physics dictates that quantum coherence collapses instantaneously in a warm and wet biological environment (about 310 K). However, a recent study has sent shockwaves through the academic world by discovering clear signal-level evidence of macroscopic quantum entanglement and multiple-quantum coherence (MQC) in the proton spin ensembles inside the human brain. An innovative paper titled "Signal-Level Witnessing of SU(1,1) Pair Dynamics in Brain Proton Spin Ensembles" was published on the preprint repository bioRxiv. Authored solely by independent researcher Christian Kerskens, this paper ruled out existing classical exchange pathways and analyzed the quantum dynamics of the brain from a new perspective. ■ SU(1,1) Quantum Squeezing Phenomenon Beyond Classical SU(2) Exchange In conventional nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) theory, spin dynamics within dipolar-coupled ensembles of biological tissues have mainly been explained by the compact symmetry SU(2) exchange pathway. SU(2) symmetry creates a classical form of dynamics where spins oscillate and exchange with each other in an energy-constrained environment. However, unusual magnetic resonance data previously acquired from the living human brain exhibited features that directly contradict this SU(2) model. Phenomena that cannot be explained by classical exchange appeared, such as signals occurring immediately without an evolution delay, or refocusing occurring at the sum rather than the difference of the two frequencies. The author of this study, Christian Kerskens, presented a new analytical framework suggesting that these anomalous signals originate from a non-compact SU(1,1) pair sector. SU(1,1) symmetry is mainly dealt with in quantum optics and is the dynamics governing the exponential amplification and quantum squeezing of signals. This is the first time this symmetry has been directly observed in a macroscopic spin ensemble. ■ The Readout Pathway Uncovering Hidden Double-Quantum (DQ) Coherence The most significant characteristic of SU(1,1) pair operators is that they possess a double-quantum (DQ) coherence order rather than zero-quantum (ZQ). In principle, typical detectors cannot directly read these multiple-quantum states. However, the researcher mathematically proved that the unique 45°-gradient-45° pulse readout block used in the experiment provides a specific coherence-transfer pathway that converts this hidden DQ pair coherence into a detectable signal. In other words, he revealed that a specific wave we read as a brain MRI signal was actually the result of an entangled double-quantum state among brain protons. ■ Quantum Proof Overcoming the 'Thermodynamic Obstruction' of 310 K Biological Temperature Another crucial achievement of this study is that it bypassed the pseudopure-state obstruction, a chronic limitation of room-temperature bulk NMR environments. In the high-temperature brain environment, thermodynamic noise is dominant, so an entangled state can never be proven with a bipartite entanglement evaluation formula that isolates and looks at only two spins. The researcher redefined the observed signal not simply as a signal of two isolated spins, but as a collective multiple-quantum coherence (MQC) signal of the entire massive spin ensemble. The observed signal acts as a powerful quantum witness indicating that the macroscopic proton pool of the brain has exceeded the pure single-mode compression limit and entered a complex cross-mode entangled structure. This paper is evaluated as having an enormous impact on the convergence of brain science and quantum biology, as it demonstrated with a rigorous physical framework the possibility that the living human brain possesses a macroscopic quantum state with countless proton spins entangled with each other through SU(1,1) dynamics.
We demonstrate that entanglement can persistently recur in an oscillating two-spin molecule that is coupled to a hot and noisy environment, in which no static entanglement can survive. The system represents a nonequilibrium quantum system which, driven through the oscillatory motion, is prevented from reaching its (separable) thermal equilibrium state. Environmental noise, together with the driven motion, plays a constructive role by periodically resetting the system, even though it will destroy entanglement as usual. As a building block, the present simple mechanism supports the perspective that entanglement can exist also in systems which are exposed to a hot environment and to high levels of decoherence, which we expect, e.g., for biological systems. Our results also suggest that entanglement plays a role in the heat exchange between molecular machines and environment. Experimental simulation of our model with trapped ions is within reach of the current state-of-the-art quantum technologies.