The core problem the technology addresses is one of resolution. Biological samples such as serum contain tens of thousands of metabolites and lipids spanning an enormous range of chemical polarities and concentrations. When these compounds are separated by liquid chromatography and fed into a mass spectrometer, many arrive at the detector at nearly the same moment and with nearly identical mass-to-charge ratios. Lipids are especially troublesome: a species such as the phospholipid PC 34:2 exists in several structurally distinct isomeric forms with identical masses, and lipids from entirely different classes can share mass values so closely that their signals overlap. To make matters worse, molecules can form multiple adducts with sodium, potassium, or hydrogen ions, and the naturally occurring heavy isotopes of carbon, nitrogen, sulphur, and oxygen create additional peaks that can masquerade as entirely different compounds. The result is a forest of ambiguous signals in which confident identification, the foundation of biomarker discovery, becomes extraordinarily difficult.

Time-of-flight mass spectrometry has been a mainstay of high-resolution analysis for decades. The principle is elegant: ions are accelerated into a vacuum tube, and because heavier ions travel more slowly, their arrival times at a detector reveal their masses. Resolution improves with the length of the flight path, since ions of slightly different mass have more time and distance to separate. Classically, this meant building longer flight tubes, an approach that quickly becomes impractical in a laboratory and, crucially, degrades signal as ions travel farther. An alternative is to bounce ions back and forth between electrostatic mirrors called reflectrons, but conventional reflectrons contain wire grids that scatter and lose ions with each reflection. Over a handful of bounces the loss is tolerable; over dozens it becomes fatal to sensitivity and mass accuracy.

The multi-reflecting time-of-flight platform, or MRT, overcomes this limitation with gridless reflectron mirrors. Ions are reflected repeatedly through a series of periodic focusing lenses, extending the effective flight path to 47 metres inside an instrument of ordinary laboratory size while maintaining signal transmission. The result is a mass resolution exceeding 200,000 full width at half maximum, combined with sub-part-per-million mass accuracy and acquisition rates of up to 30 spectra per second. That combination of speed and resolution is what sets the platform apart. Fourier-transform instruments such as Orbitraps and ion cyclotron resonance analysers can achieve comparable or higher resolution, but they typically require scan times of around one second, which is far too slow to adequately sample the narrow two-to-three-second chromatographic peaks produced by modern ultra-high-performance liquid chromatography. The MRT, by contrast, collected 28 data points across a six-second peak in the demonstration study, providing the peak definition needed for both qualitative identification and quantitative analysis.

To put the instrument through its paces, the researchers analysed serum samples from eight patients recruited into the Manchester Allergy, Respiratory, and Thoracic Surgery Biobank COVID-19 cohort. The patients spanned a range of disease severity, from mild and convalescent infections to severe, active disease requiring intensive care, and were classified using the Manchester COVID-19 Severity Score, a clinical tool based on the level of respiratory intervention each patient required. Lipids and polar metabolites were extracted from the serum using a methyl-tert-butyl ether protocol and separated on an amide column over a rapid ten-minute gradient, with the mass spectrometer acquiring data in both positive and negative electrospray ionisation modes using data-independent acquisition.

The technical payoff was most vivid in the lipid region of the spectra. At a chromatographic peak eluting at 1.5 minutes, the instrument recorded four major ions. The base peak at mass-to-charge ratio 758.57019 was annotated as the phospholipid PC 34:2, but the next most intense peak, nominally at 760.58, resolved into two distinct signals separated by less than 0.01 daltons. One was the doubly carbon-13-labelled isotope of PC 34:2; the other was the monoisotopic peak of a co-eluting lipid, PC 34:1. The measured resolution of this region was 224,770, and simulations showed that even a conventional instrument operating at 100,000 resolution could not have separated the two. Similar deconvolution was achieved for the potassium adducts of the same lipids, where heavy and light isotopes of potassium and carbon combined to produce a tangle of overlapping signals that only the fine isotopic detail captured by the MRT could untangle. Because each element carries a characteristic isotope abundance pattern, this fine structure acts as a molecular fingerprint, providing an independent check on elemental composition that goes far beyond mass matching alone.

Mass accuracy proved equally transformative for compound annotation. Conventional quadrupole time-of-flight instruments typically report mass errors of one to three parts per million, and Orbitrap platforms around one to two parts per million at high resolution. The MRT delivered errors between 21 and 134 parts per billion across annotated compounds, roughly an order of magnitude tighter. This matters practically because database searching scales with the mass tolerance applied: a feature measured at 597.28739 returned nine candidate identifications when searched at two parts per million but only two when the filter was tightened to half a part per million, corresponding to isomeric forms of taurochenodeoxycholate sulphate. Narrower search spaces mean fewer false positives and far less manual curation, a persistent burden in large-scale metabolomics.

Applied to the patient cohort, the platform revealed metabolic differences associated with disease severity. Patients with severe, active infections showed broadly similar serum lipidome profiles, generally with lower feature abundance than a convalescent patient and one with mild disease, whose profiles clustered together. One severely ill patient stood apart with 152 unique mass features, compared with an average of 37.5 for the other patients. Among the annotated features in this individual were taurochenodeoxycholate sulphate and glycoursodeoxycholic acid, both bile acid derivatives. Sulphated bile acids have previously been reported as elevated in severe COVID-19 and linked to sepsis and renal dysfunction, and the patient’s clinical record of kidney failure and hypercholesterolemia was consistent with these findings. The same patient’s serum contained iohexol, an iodinated contrast agent normally cleared within 24 hours, which the researchers attributed to a recent CT scan compounded by renal failure delaying excretion. Perhaps most intriguingly, a feature was annotated as sphingofungin A, a sphingoid metabolite of the fungus Aspergillus fumigatus, the most common cause of COVID-19-associated pulmonary aspergillosis, a dangerous opportunistic infection estimated to affect roughly one in three mechanically ventilated patients. The patient had been ventilated, though the authors caution that the diagnosis could not be confirmed retrospectively.

The authors are careful to frame the work as a demonstration rather than a definitive clinical study. With only eight patients, one of whom was excluded on technical grounds, the findings cannot establish biomarkers or explain mechanisms, and the team acknowledges that the challenges of much larger metabolomics studies remain to be addressed. Several of the study’s authors are employed by Waters Corporation, the instrument’s manufacturer, a conflict of interest disclosed in the paper. Nevertheless, the proof of principle is compelling: the MRT platform resolved overlapping lipid species that would have gone undetected on conventional time-of-flight or electrostatic trap instruments, matched its annotations to the patients’ documented clinical histories, and did so at acquisition speeds compatible with the high-throughput analysis that well-powered clinical and epidemiological cohorts demand. If the technology scales as its developers hope, it could sharpen the entire pipeline of biomarker discovery, from the first chromatographic separation to the final confident assignment of a molecule’s identity, turning the chemical noise of human blood into interpretable clinical signal.

Subject of Research: High-resolution multi-reflecting time-of-flight mass spectrometry for metabolite and lipid identification in COVID-19 patient serum

Article Title: Multi-reflecting time-of-flight mass spectrometry enables high-accuracy metabolite identification in a demonstration study using serum samples from COVID-19 patients

Article References: King, A., Matthews, E., Maker, G., Trengove, R., Shareef, S., Fowler, S., Felton, T., Simpson, A., Palmer, M., Gethings, L. A., Plumb, R. S., & Mills, E. N. C. (2026). Multi-reflecting time-of-flight mass spectrometry enables high-accuracy metabolite identification in a demonstration study using serum samples from COVID-19 patients. Metabolomics, 22(5), Article 168. https://doi.org/10.1007/s11306-026-02539-w

Image Credits: AI Generated

DOI: 10.1007/s11306-026-02539-w

Keywords: metabolomics, lipidomics, mass spectrometry, time-of-flight, COVID-19, biomarkers, bile acids, isotopic fine structure, liquid chromatography, serum, renal dysfunction, aspergillosis

The core difficulty with position verification is that ordinary distance measurements are fundamentally based on trust. Radar, GPS, and time-of-flight ranging all rely on the assumption that the device being located responds honestly and that the signals it returns are genuine. A spoofing attacker can exploit this by relaying messages, predicting challenge responses, or replaying recorded signals faster than physics should allow. Classical cryptography alone cannot close these loopholes, because any classical challenge-response scheme can, in principle, be simulated or forwarded by a sufficiently capable adversary. What the new work shows is that by encoding challenges in quantum states, specifically coherent states, the kind of light produced by ordinary lasers, and by enforcing the relativistic speed limit on information, a verifier can confirm a prover’s location with security guarantees that no classical protocol can match.

The protocol builds on a concept known as relativistic position verification, which has been discussed theoretically for more than a decade. The idea is elegant in its use of special relativity. A verifier sends a challenge signal to the claimed position of a prover, and the prover must respond within a strict time window determined by the speed of light. If the prover is genuinely at the claimed position, the round-trip timing works out precisely. If the prover is anywhere else, the finite speed of light makes it impossible to receive the challenge and return a correct response in time. The catch, historically, has been that a single relativistic check can be defeated by multiple colluding adversaries who surround the claimed position and share information, provided the challenge itself carries no quantum advantage. The new protocol confronts this collusion problem directly by making the challenge a quantum state that cannot be perfectly copied or measured without disturbance.

Coherent states occupy a special place in quantum optics. They are the closest quantum states to classical light, describing the output of an ideal laser, and they are famously robust: a beam splitter tapping a fraction of a coherent state leaves the remaining light in another coherent state, undisturbed. This resilience is precisely why coherent states are the workhorses of optical communication. But it also means they cannot be protected by the no-cloning theorem in the same dramatic way that single photons can. The researchers’ insight was to design a verification scheme in which the security does not depend on detecting eavesdropping through disturbance, but rather on the statistical structure of the coherent-state challenge combined with relativistic timing constraints. An attacker who tries to intercept, measure, and forward the challenge gains only limited information within the light-speed-bounded window, and that limitation translates into a quantifiable, provable bound on the probability of successful spoofing.

In the experimental demonstration, the team implemented the protocol using quantum optical equipment in a laboratory setting that emulated the geometry of a multi-verifier network. Verifiers at separated reference points prepared coherent-state challenges and sent them toward the claimed position of a prover. The prover, located at the intersection point defined by the overlapping signals, was required to perform a joint measurement on the arriving light and return a response that depended on the full quantum content of the challenges. The verifiers then checked both the correctness of the response and its arrival time against the relativistically mandated schedule. Only a prover genuinely at the claimed spacetime point, with access to the complete quantum information carried by the coherent pulses, could satisfy both conditions simultaneously with high probability.

The measurement statistics from the experiment confirmed the central theoretical prediction. Honest provers at the correct location passed the verification test with high probability, while simulated attacks, in which adversaries positioned away from the claimed point attempted to collaborate and cheat the timing and content checks, succeeded only with probabilities bounded well below the levels required to break the protocol. The experiment thereby elevated relativistic position verification from a theoretical proposal with idealized assumptions to a demonstrated capability built from realistic optical components. Because coherent states are exactly what standard telecommunications lasers produce, the result carries an unusually direct path toward practical deployment in fiber networks and free-space optical links.

The security implications extend across several domains of modern technology. In satellite navigation, position verification could harden global positioning systems against spoofing attacks, a threat that has been demonstrated against civilian GPS receivers and poses risks to aviation, maritime shipping, and autonomous vehicles. In distributed computing and blockchain systems, verifiable position could anchor the physical identity of nodes, preventing adversaries from masquerading as geographically distributed participants. In quantum networks, where future quantum internet nodes will exchange entanglement and secret keys over continental distances, confirming that a node is physically where it claims to be adds a layer of authentication that no certificate or cryptographic key alone can provide. The protocol essentially gives the physical layer of communication a cryptographic guarantee derived from the laws of nature rather than from computational assumptions.

What makes the achievement scientifically notable is the way it reconciles two apparently competing demands. Quantum protocols for position verification have often relied on fragile single-photon states or entanglement, which are difficult to distribute over long distances and easily degraded by loss. Relativistic schemes, conversely, have been robust in their signals but vulnerable to collusion attacks. By choosing coherent states, the experimenters selected the most loss-tolerant, telecom-compatible quantum states available, and then recovered security against collusion through a careful protocol design that exploits the interplay between the quantum statistics of the light and the strict causal structure imposed by relativity. The result is a scheme whose ingredients are mundane, laser light and precise clocks, but whose guarantees are anything but.

The work also contributes to a broader conceptual shift in quantum information science: the recognition that spacetime structure itself is a computational and cryptographic resource. Just as entanglement enables tasks impossible classically, the light cone structure of relativistic spacetime constrains what any attacker can know and when they can know it, and protocols that weave quantum states through this causal fabric inherit guarantees rooted in physics. Position verification is perhaps the most natural application of this principle, because position is defined by spacetime, but researchers have begun exploring related ideas in secure timing, delegated quantum computation, and verifiable quantum communication. The new demonstration provides an experimental anchor for this emerging field, showing that the theory can be reduced to working hardware.

Challenges remain before such systems secure real-world infrastructure. Laboratory demonstrations operate over short distances with controlled timing, whereas field deployment will demand picosecond-level clock synchronization across verifier stations, management of atmospheric and fiber-induced noise, and careful analysis of loss, which affects coherent states in ways that must be folded into the security proofs. Scaling the number of verifiers and the distance to the prover will require engineering advances in optical timing distribution and high-speed quantum-light detection. Yet the direction is clear. The experiment demonstrates that verifying where someone is, without trusting anything they say, can be achieved by combining the most ordinary light in the universe with the most fundamental speed limit in nature. In doing so, it turns a century of physics, from Einstein’s postulates to the quantum theory of light, into a practical answer to a deceptively simple question: can you prove where you are? The answer, it turns out, is yes, if your answer travels at the speed of light and carries the quiet statistical fingerprint of a coherent state.

Subject of Research: Relativistic position verification using coherent quantum states of light

Article Title: Relativistic position verification with coherent states

Article References: Fan-Yuan, G.-J., Shan, Y.-G., Zhang, C., Wang, Y.-L., Fan, Y.-X., Xie, W.-X., He, D.-Y., Wang, S., Yin, Z.-Q., Chen, W., Fu, S.-N., Guo, G.-C., & Han, Z.-F. (2026). Relativistic position verification with coherent states. Nature Physics. https://doi.org/10.1038/s41567-026-03439-5

Image Credits: AI Generated

DOI: 10.1038/s41567-026-03439-5

Keywords: position verification, coherent states, quantum optics, relativistic cryptography, spoofing attacks, speed of light, quantum communication, laser light, quantum networks, spacetime, time-of-flight, security protocols