![]() ![]() If the first pulse didn’t contain any photons, the dot blocked subsequent photons from getting through. The first light pulse acts like a key, opening the door for the second photon to enter the chip. The team observed that a single photon could, by interacting with the dot, control the transmission of a second light pulse through the device. However, in this device, a single photon gets trapped for a long time, registering its presence in the nearby dot. In a normal environment, such dim light might barely register. To test that the chip operated like a transistor, the researchers examined how the device responded to weak light pulses that usually contained only one photon. “This allows a single photon to switch a bigger stream of photons, which is essential for our device to be considered a transistor.” “In a single-photon transistor the quantum dot memory must persist long enough to interact with each photonic qubit,” says Shuo Sun, the lead author of the new work who is a Postdoctoral Research Fellow at Stanford University. The dot can effectively tap into that memory to mediate photon interactions-meaning that the actions of one photon affect others that later arrive at the chip. ![]() Analogous to conventional computer memory, the dot stores information about photons as they enter the device. Light entering the chip bounces around and gets trapped by the hole pattern a small crystal called a quantum dot sits inside the area where the light intensity is strongest. The photonic chip is made from a semiconductor with numerous holes in it, making it appear much like a honeycomb. “Software running on a quantum computer would use a series of such operations to attain exponential speedup for certain computational problems. “Using our transistor, we should be able to perform quantum gates between photons,” says Waks. The device, described in Science, is compact: Roughly one million of these new transistors could fit inside a single grain of salt, and it’s also fast – able to process 10 billion photonic qubits every second! Now, researchers at the Joint Quantum Institute (JQI), led by JQI Fellow Edo Waks have cleared this hurdle and demonstrated the first single-photon transistor using a semiconductor chip. However, making a quantum transistor triggered by light has been challenging because it requires that the photons interact with each other, something that doesn’t ordinarily happen on its own. Photons have added appeal because they can swiftly shuttle information over long distances and they are compatible with fabricated chips. Scientists can use many kinds of quantum particles as qubits, even the photons that make up light. They used a single photon, stored in a quantum memory, to toggle the state of other photons. Researchers demonstrate the first single-photon transistor using a semiconductor chip. That’s because quantum information carriers, dubbed qubits, have to follow different rules laid out by quantum physics. But the design constraints for this new technology are stringent, and try as we might even today’s most advanced processors can’t be repurposed as quantum devices. Transistors are tiny switches that form the bedrock of modern computing-billions of them route electrical signals around inside a smartphone, for instance, and future Quantum computers, that are hundreds of millions of times more powerful than today’s computers, will need analogous hardware to manipulate quantum information. And as transistors go it’s unlikely anyone will be beating that record any time soon. What makes the breakthrough even more extraordinary though is the fact that, because of a geeky physics “fact,” photos aren’t actually particles they’re waves which actually means that for the first time scientists have created a transistor that, literally, has no size. ![]() But, after a new announcement, even those transistors appear huge after scientists developed a transistor that’s just a single photon in size. However, as it gets more expensive, which is the real problem with Moore’s Law, to create ever smaller silicon based transistors for computer chips researchers all around the world have found ways to push the limits of transistors so much so that today we have 5nm, 3nm, 1nm, 0.5nm, liquid, molecular, and even single atom transistors in the labs. Moore’s Law is slowing down, meaning that decades worth of continuous improvements in computing power are coming to an end – so we’re told. Interested in the Exponential Future? Join our XPotential Community, future proof yourself with courses from our XPotential Academy, connect, watch a keynote, or browse my blog. By Matthew Griffin Computing 26th July 2020 WHY THIS MATTERS IN BRIEF Transistors are found in every electronic device on Earth, but Moore’s Law is running out of steam, and now researchers have developed the world’s smallest transistor – with zero size. ![]()
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