On March 18th, astronauts Sunita Williams and Butch Wilmore returned from the International Space Station (ISS) after their unscheduled nine-month stay in orbit. There has been much concern expressed around Williams and Wilmore’s health, having survived the harsh conditions of outer space. Yet if anything, the duo came out younger than we did in the interim period – thanks to strange physics that we typically don’t encounter daily.

Williams and Wilmore lived in a weak gravitational environment throughout their stay up in space; at the least compared to everyone else on earth. At that altitude 450 km above the surface, Einstein’s theory of relativity came to play – slowing down time for the astronauts.

When clocks run slow

In Einstein’s general theory of relativity, gravity is better explained as the distortive effect in an abstract continuum called space-time. This is quite distinct from Newton’s explanation of gravity, of invisible attractive forces emanating from masses themselves. In relativity, matter and energy twist both space as well as time. Imagine a thin fabric of material. Mass and energy are akin to heavy objects producing depressions in them.

Although we don’t encounter relativistic effects in our everyday encounters in life, their effects are subtle but measurable. The difference in gravity’s strength here produced a noticeable time dilation. Stronger the gravity, the slower does time flow for that person. This means people on earth aged slightly more with respect to the astronauts. This should mean that astronauts spending time up in space should have aged faster due to gravitational time dilation alone.

Except, there is yet another source of time dilation that contributes to aging – and that is, velocity. The ISS zips through low-earth orbit at speeds clocking nearly 28,800 km/h – or 8 km/s. That’s faster than a typical intercontinental ballistic missile when it’s mid-way in its journey. Space-time can distort tangibly when an object possesses incredible energy – and not just gravity. Time dilation from the ISS hurtling at such tremendous speeds, outsized the effect from earth’s gravity. And the resultant time flow would be slower than usual.

In effect, the duo aged slower, by approximately 0.0075 seconds. Virtually, there is no difference as you might notice. But with a good atomic clock though, time dilation can be demonstrated as a subtle, yet measurable effect. In fact, engineers have exploited the effect to solve technical problems arising with global positioning system (GPS) satellites, to coordinate and ensure positional accuracy. The high-precision atomic clocks on-board GPS satellites help software correct for latency errors, accounting for time dilation as well.

The ability to control the behaviour of individual cells has long been a goal of scientists studying cell development. MIT researchers have now developed a method to manipulate how a single cell moves and changes shape, using light. This breakthrough, which could have far-reaching applications in synthetic biology and medicine, was demonstrated in egg cells from starfish—a common model for understanding cell behaviour during development.

The team, led by Nikta Fakhri, focused on an enzyme within the starfish egg cell that triggers a cascade of movements. By genetically engineering a light-sensitive version of this enzyme, the researchers were able to use light to direct the cell’s motion in precise patterns.

“We found that the light successfully triggered the enzyme, which in turn prompted the cells to jiggle and move in predictable patterns,” says Fakhri, an associate professor of physics at MIT. “For instance, we could stimulate cells to exhibit small pinches or sweeping contractions, depending on the pattern of light we induced. We could even shine light at specific points around a cell to stretch its shape from a circle to a square.”

The findings, set to be published in Nature Physics, open up exciting possibilities for future medical and synthetic cell applications. The researchers envision using this technology to design cells that could respond to light for therapeutic purposes, such as “patch” cells that contract to help close wounds or drug-delivering cells that release medication only when illuminated at specific locations in the body.

Fakhri continues, “By revealing how a light-activated switch can reshape cells in real time, we’re uncovering basic design principles for how living systems self-organize and evolve shape.”

The research team includes MIT’s Jinghui Liu, Yu-Chen Chao, and Tzer Han Tan, alongside collaborators from Ludwig Maximilian University of Munich, Saarland University, and the Whitehead Institute for Biomedical Research.

Exploring the Starfish Model

Fakhri’s group specializes in understanding the physical dynamics that drive cell growth, especially the role of symmetry in cell development. The starfish, known for its distinct stages of symmetry, is an ideal organism for studying the signalling processes that guide cell organization.

“A starfish is fascinating because it starts with a symmetrical cell and eventually develops into an adult with pentameral symmetry,” Fakhri explains. “There are many signalling events along the way that direct how the cell organizes itself into more complex structures.”

The team’s earlier research identified a key “circuitry” in the starfish egg cell that regulates its movement and shape. This circuitry involves an enzyme called GEF, which, when activated, triggers a protein called Rho. Rho plays a crucial role in regulating cell mechanics by binding to the cell’s membrane and initiating the formation of muscle-like fibres that enable the cell to contract and move.

Harnessing Light to Control Cell Movement

In this new study, the team turned to optogenetics, a technique that uses light to control genetically engineered cellular components. They created a light-sensitive version of the GEF enzyme and injected it into egg cells harvested from starfish. The cells, now capable of producing the light-sensitive enzyme, were placed under a microscope, and the researchers applied light in different patterns to observe how the cells responded.

By targeting specific areas of the cell with light, they were able to activate the enzyme, triggering the Rho protein to form fibers and cause the cell to move. This allowed the team to control the cell’s shape, even morphing it from a circle into a square. Additionally, they discovered that shining light in a single spot could initiate sweeping contractions within the cell, providing even more precise control over its behaviour.

“We realized this Rho-GEF circuitry is an excitable system, where a small, well-timed stimulus can trigger a large, all-or-nothing response,” Fakhri says. “By illuminating either the entire cell or just a small region, we can control how the cell responds and causes contraction or pinching.”

The researchers also developed a theoretical framework to predict how cells would change in response to light stimuli. This new understanding of cellular “excitability” could have important implications for fields like developmental biology, wound healing, and synthetic biology.

Future Applications in Synthetic Biology

“This work provides a blueprint for designing programmable synthetic cells,” Fakhri explains. “By controlling cell shape in real time, we can potentially design cells that perform specific tasks in the body when activated by light. This could lead to new biomedical applications, from targeted drug delivery to tissue repair.”

The ability to control cell behaviour with light opens up exciting possibilities for future research and applications, offering a new way to explore how cells shape themselves during development and how we might harness these processes for therapeutic use.

Quantum computers have the potential to solve complex problems that current classical supercomputers cannot. As quantum technology progresses, a key challenge is developing effective ways for quantum processors to communicate with each other efficiently. Traditional methods for interconnecting superconducting quantum processors use “point-to-point” connections, which are limited by error rates that increase as more transfers occur. MIT researchers have taken a major step toward overcoming these limitations by developing a new interconnect device that supports scalable, “all-to-all” communication between quantum processors.

The breakthrough, described in a paper published in Nature Physics, involves a network of two quantum processors linked by an interconnect that sends microwave photons—particles of light that carry quantum information—back and forth on demand. The device includes a superconducting waveguide that can shuttle photons between processors and allows for the coupling of multiple modules, enabling more efficient information transfer across a scalable network.

“In the future, a quantum computer will probably need both local and nonlocal interconnects. Local interconnects are natural in arrays of superconducting qubits. Ours allows for more nonlocal connections. We can send photons at different frequencies, times, and in two propagation directions, which gives our network more flexibility and throughput,” said Aziza Almanakly, the lead author of the paper and a graduate student in MIT’s Engineering Quantum Systems group.

This interconnect device is a significant advancement in the quest to build a distributed network of quantum processors. By generating remote entanglement—quantum correlations between distant processors—it paves the way for a large-scale, interconnected quantum computing system.

“Pitching and catching photons enables us to create a ‘quantum interconnect’ between nonlocal quantum processors, and with quantum interconnects comes remote entanglement,” said senior author William D. Oliver, a professor of Electrical Engineering and Computer Science at MIT. “Generating remote entanglement is a crucial step toward building a large-scale quantum processor from smaller-scale modules.”

The researchers achieved this by connecting two quantum modules, each composed of four qubits that interface with the waveguide to emit and absorb photons. By using carefully timed microwave pulses, they directed photons to propagate through the waveguide in either direction, establishing remote entanglement between two modules. This entanglement allows quantum operations to occur across distant, disconnected processors.

“We can use this architecture to create a network with all-to-all connectivity. This means we can have multiple modules, all along the same bus, and we can create remote entanglement among any pair of our choosing,” explained Beatriz Yankelevich, a graduate student and co-author of the paper.

One of the major hurdles in quantum communication is ensuring the photon is absorbed with high efficiency at the receiving module. To tackle this, the team used a reinforcement learning algorithm to optimize the photon’s shape, improving the absorption efficiency to over 60 percent. This efficiency is enough to confirm that the entanglement is successful—a critical milestone in building a robust quantum network.

This development could eventually lead to advancements in quantum internet systems, where quantum processors across vast distances can share information securely. While this demonstration marks a significant achievement, the team envisions further refinements, such as optimizing photon propagation paths and reducing protocol errors.

“In principle, our remote entanglement generation protocol can also be expanded to other kinds of quantum computers and bigger quantum internet systems,” Almanakly said, hinting at the vast potential for this technology to shape the future of computing.

As quantum networks continue to evolve, this research could be a foundational step toward realizing a new era of distributed quantum computing