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26 DESIGN007 MAGAZINE I AUGUST 2021 • Isola I-Speed MS, for instance, is mechanical spread glass that is an improvement especially if 2-ply construction is employed. • Fly-over cables remove the signals off the backplane entirely, from chip to off-system connector. • Using cables for 56 Gbps signals cuts losses by about half compared to PCB traces. • e role of fly-over cables is to isolate signals from the limitations of the PCB materials. • Fly-over cables are ideal for 28, 56 and 112 Gbps data rate serial links. • e shi from NRZ to PAM4 modulation encoding has made it extremely difficult to meet jitter and noise requirements over any useful length of board. • PAM4 is a more viable solution for high- frequency serial communications. • Fly-over technology provides perfor- mance and cost advantages compared to lossy PCBs, with up to 112 Gbps performance at 150 mm cable length. • With the signaling rate increasing, electrical channels like PCB traces or copper cable both have bandwidth limitations. • Optical fiber cables can be used to transmit high bandwidth data over both short and long distances. Resources 1. Twinax Flyover Cable Systems | System Optimi- zation | Samtec 2. "Flyover Cables: Inevitable, but Not Easy," by Patrick Mannion 3. "Understanding NRZ and PAM4 Signaling," by Brian Niehoff 4. SI List, by Scott McMorrow, Samtec Barry Olney is managing director of In-Circuit Design Pty Ltd (iCD), Australia, a PCB design service bureau that specializes in board- level simulation. The company developed the iCD Design Integrity software incorporating the iCD Stackup, PDN, and CPW Planner. The software can be downloaded at www.icd.com.au. To read past columns or con- tact Olney, click here. A team of scientists at Los Alamos National Labo- ratory propose that modulated quantum metasur- faces can control all properties of photonic qubits, a breakthrough that could impact the fields of quan- tum information, communications, sensing and imaging, as well as energy and momentum harvest- ing. The results of their study were released in the journal Physical Review Letters, published by the American Physical Society. Metasurfaces are ultrathin structures that can manipulate light in ways not usually seen in nature. In this case, the team developed a metasurface that looked like an array of rotated crosses, which they can then manip- ulate with lasers or electrical pulses. They then proposed to shoot a single photon through the metasurface, where the photon splits into a superposition of many colors, paths, and spin- ning states that are all intertwined, generating so- called quantum entanglement—meaning the single photon is capable of inheriting all these different properties at once. Harnessing photons that exist in the vacuum and shooting them in one direction should create pro- pulsion in the opposite direction. Similarly, stirring the vacuum should create rotational motion from the twisted photons. Struc- tured quantum light could then one day be used to generate mechanical thrust, using only tiny amounts of energy to drive the meta- surface. (Source: Los Alamos National Laboratory) New Quantum Research Gives Insights Into Mastering Quantum Light