A recent collaboration between researchers led by Andreas Nunnenkamp from the University of Vienna and Ewold Verhagen from AMOLF, Amsterdam, has achieved a breakthrough in the field of signal routing. Their work, published in Nature Physics, introduces a novel concept called “quadrature nonreciprocity,” which enables unidirectional transport of signals without the need for bulky and lossy devices or magnetic fields.
Traditionally, devices that allow signals to travel in one direction, such as isolators or circulators, have relied on magnetic fields and exhibited significant drawbacks. The team’s research offers an alternative approach that is more compact and does not require time-reversal breaking.
Quadrature nonreciprocity leverages the interference between two distinct physical processes. This phenomenon introduces a dependence on the phase, or quadrature, of the signal, enabling unidirectional transmission. Dr. Clara Wanjura, the theoretical lead author, explains that these devices create a “dual carriageway” for signals, where one quadrature travels in one direction and the other in the opposite direction. Time-reversal symmetry ensures that the quadratures always move pairwise in separate lanes.
To demonstrate this concept, the experimental team at AMOLF employed a nanomechanical system using small silicon strings controlled by laser light. By exerting forces on the strings, the laser light facilitated interactions between their different vibration modes.
Dr. Jesse Slim, the experimental lead author, emphasizes the development of a versatile experimental toolbox that enabled the manipulation of the required interactions for quadrature nonreciprocity. This allowed them to observe the resulting unidirectional transport of signals experimentally.
The implications of this research are significant, as it opens up new possibilities for signal routing and quantum-limited amplification. These findings have potential applications in quantum information processing and sensing, addressing the needs of more flexible signaling devices in various practical scenarios.