[2023 APCTP Spring Colloquium] Wormholes and quantum entanglement.
Date: 10 March, 2023
Speaker: Prof. Juan Maldacena.
We describe various types of wormholes in general relativity. We willmention which wormholes are allowed and which ones are forbidden, bothclassically and quantum mechanically. We will describe the connectionbetween wormholes and entanglement, in the particular case of entangledblack holes.
PRESS RELEASE — To perform quantum computations, quantum bits (qubits) must be cooled down to temperatures in the millikelvin range (close to-273 Celsius), to slow down atomic motion and minimize noise. However, the electronics used to manage these quantum circuits generate heat, which is difficult to remove at such low temperatures. Most current technologies must therefore separate quantum circuits from their electronic components, causing noise and inefficiencies that hinder the realization of larger quantum systems beyond the lab.
Researchers in EPFL’s Laboratory of Nanoscale Electronics and Structures (LANES), led by Andras Kis, in the School of Engineering have now fabricated a device that not only operates at extremely low temperatures, but does so with efficiency comparable to current technologies at room temperature.
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A group of physicists wants to use artificial intelligence to prove that reality doesn’t exist. They want to do this by running an artificial general intelligence as an observer on a quantum computer. I wish this was a joke. But I’m afraid it’s not.
Paper here: https://quantum-journal.org/papers/q–…
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One of the greatest mysteries of science could be one step closer to being solved. Approximately 80% of the matter in the universe is dark, meaning that it cannot be seen. In fact, dark matter is passing through us constantly—possibly at a rate of trillions of particles per second.
We know it exists because we can see the effects of its gravity, but experiments to date have so far failed to detect it.
Taking advantage of the most advanced quantum technologies, scientists from Lancaster University, the University of Oxford, and Royal Holloway, University of London are building the most sensitive dark matter detectors to date.
Recent observations by ESA’s XMM-Newton and NASA ’s Chandra have revealed three unusually cold, young neutron stars, challenging current models by showing they cool much faster than expected.
This finding has significant implications, suggesting that only a few of the many proposed neutron star models are viable, and pointing to a potential breakthrough in linking the theories of general relativity and quantum mechanics through astrophysical observations.
Discovery of unusually cold neutron stars.
Researchers at the Paul-Drude-Institute for Solid State Electronics (PDI) have observed a novel modulation regime characterized by the emergence of previously unseen “acceleration beats” in a modulated semiconductor-based laser.
As they detail in a paper published today in Nature Communications, the key—and somewhat counterintuitive—feature of this novel regime is the ability to coherently manipulate quantum systems using modulation periods longer than the coherence time, provided that the modulation amplitude is large enough.
Harmonic modulation of light sources, such as lasers, is the cornerstone of many modern and emergent telecommunications technologies. In this regard, two regimes of modulation are well-known: the adiabatic regime and the non-adiabatic regime.
Scientists have made a significant breakthrough in creating a new method for transmitting quantum information using particles of light called qudits. These qudits promise a future quantum internet that is both secure and powerful. The study is published in the journal eLight.
Traditionally, quantum information is encoded on qubits, which can exist in a state of 0, 1, or both at the same time (superposition). This quality makes them ideal for complex calculations but limits the amount of data they can carry in communication. Conversely, qudits can encode information in higher dimensions, transmitting more data in a single go.
The new technique harnesses two properties of light—spatial mode and polarization—to create four-dimensional qudits. These qudits are built on a special chip that allows for precise manipulation. This manipulation translates to faster data transfer rates and increased resistance to errors compared to conventional methods.
Is nature really as strange as quantum theory says—or are there simpler explanations? Neutron measurements at TU Wien prove that it doesn’t work without the strange properties of quantum theory.
Can a particle be in two different places at the same time? In quantum physics, it can: Quantum theory allows objects to be in different states at the same time—or more precisely: in a superposition state, combining different observable states. But is this really the case? Perhaps the particle is actually in a very specific state, at a very specific location, but we just don’t know it?
The question of whether the behavior of quantum objects could perhaps be described by a simple, more classical theory has been discussed for decades. In 1985, a way of measuring this was proposed: the so-called “Leggett-Garg inequality.” Any theory that describes our world without the strange superposition states of quantum theory must obey this inequality.
In a single leap from tabletop to the microscale, engineers at Stanford University have produced the world’s first practical titanium-sapphire laser on a chip.
Researchers have developed a chip-scale Titanium-sapphire laser that is significantly smaller and less expensive than traditional models, making it accessible for broader applications in quantum optics, neuroscience, and other fields. This new technology is expected to enable labs to have hundreds of these powerful lasers on a single chip, fueled by a simple green laser pointer.
As lasers go, those made of Titanium-sapphire (Ti: sapphire) are considered to have “unmatched” performance. They are indispensable in many fields, including cutting-edge quantum optics, spectroscopy, and neuroscience. But that performance comes at a steep price. Ti: sapphire lasers are big, on the order of cubic feet in volume. They are expensive, costing hundreds of thousands of dollars each. And they require other high-powered lasers, themselves costing $30,000 each, to supply them with enough energy to function.
