Quantum Computers and Heisenberg’s Uncertainty Principle
Marijan Murat/DPA/Alamy
The Heisenberg Uncertainty Principle imposes limits on the precision of measuring specific properties of quantum entities. However, recent research suggests that utilizing quantum neural networks may allow scientists to circumvent this barrier.
For instance, when analyzing a chemically relevant molecule, predicting its properties over time can prove challenging. Researchers must first assess its current characteristics, but measuring quantum properties often leads to interference between measurements, complicating the process. The uncertainty principle asserts that certain quantum attributes cannot be accurately measured at the same time; for example, gaining precise momentum data can distort positional information.
According to Zhou Duanlu from the Chinese Academy of Sciences, recent mathematical insights indicate that quantum neural networks may address these measurement challenges more effectively.
Zhou’s team approached this issue from a practical standpoint. For optimal performance of quantum computers, understanding the properties of qubits—quantum computing’s fundamental components—is crucial. Typical operations, akin to dividing by 2, are employed to yield information about qubits. Yet, the uncertainty principle presents challenges akin to the incompatibility encountered when attempting to execute several conflicting arithmetic operations simultaneously.
Their findings propose that leveraging quantum machine learning algorithms, or Quantum Neural Networks (QNNs), could effectively resolve the compatibility issues inherent to quantum measurements.
Notably, these algorithms rely on randomly selected steps from a predefined set, as shown in previous studies. Zhou et al. demonstrated that introducing randomness into QNNs can enhance the accuracy of measuring a quantum object’s properties. They further extended this approach to simultaneously measure various properties typically constrained by the uncertainty principle, using advanced statistical techniques to aggregate results from multiple random operations for improved precision.
As noted by Robert Fan, this capability to measure multiple incompatible properties swiftly could accelerate scientific understanding of specific quantum systems, significantly impacting quantum computing fields in chemistry and material sciences, as well as large-scale quantum computer research.
The practicality of this innovative approach appears promising, though its effectiveness will hinge on how it compares against other methodologies employing randomness to facilitate reliable quantum measurements, Huang asserts.
If you’ve taken a physics class, you likely have “memorable” instances of measuring light speed, spending hours setting mirrors, lenses, and light sources just right to achieve the result: just under 300 million meters per second. This figure is a fundamental constant in physics and vital for comprehending the universe.
When observing space, light is our primary resource. While we have other means, like gravitational waves, they currently offer limited insights, so I might be exaggerating a tad. Almost all advancements in astronomy and cosmology derive from collecting light that has traversed from the edge of reality over millions, or even billions, of years. Light from our nearest star takes over four years to reach us. The duration it takes for light to travel may be one of the most practical yet least intuitive aspects of physics.
Humans have debated light’s speed long before we truly understood light itself. For centuries, many intellectuals believed that the glowing in certain animals’ eyes at particular angles indicated they emitted light, resembling a lantern. Nonetheless, they debated whether light traveled instantaneously or required time to propagate, a question not thoroughly tested until the 17th century.
An early endeavor to quantify it involved placing a lantern at a distance and measuring the time difference between it lighting up and the observer seeing the light. This method proved ineffective (Galileo and his peers failed to attain conclusive measurements because the lantern was too close), leading scientists to explore more complex and accurate approaches. The first effective instrument was developed in 1675 by Ole Römer while measuring Jupiter’s moon Io’s orbital period. He observed that the period seemed to vary as the distance from Earth to Jupiter fluctuated, which seemed perplexing. Why would Io’s orbit correlate with Earth’s positioning? The only variation was the time it took for light to travel from Io to Earth, diminishing as the two grew closer. A colleague, Christian Huygens, calculated that light’s speed was around 220,000,000 meters per second. Although this estimate lacked precision due to unknown earthly movements, it established a foundation for later refinements. By the early 18th century, measurements were within a few percent of the current consensus of light’s speed in vacuum: 299,792,458 meters per second.
This prompts two inquiries: Why is the speed of light seemingly arbitrary, and why is there a speed limit at all? The first question is straightforward, linked to our units. Meters and seconds (or miles and hours) originated from human experiences. For instance, a mile equals 1,000 steps and has no relation to fundamental constants. The second question is more complex, entwined with special relativity.
The answer lies in perhaps the most recognizable equation: e=mc2. This equation implies that energy and mass can be interchanged. When objects move at extremely high or relativistic speeds, I like to think of them possessing momentum, blending mass and velocity. To increase an object’s speed, we must continually supply more energy. A massive object achieving light speed would require infinite momentum, equating to infinite energy or mass. This situation is unattainable. As an object nears light speed, its mass escalates, making further acceleration unfeasible. Light, having no mass, circumvents this dilemma.
Moreover, special relativity illustrates that an outside, stationary observer would perceive something quite unusual. When an object travels at relativistic speeds, time appears to slow down from an external viewpoint. If I were moving away from you at 99% of light speed, I’d observe my aging decelerating. This phenomenon is termed time dilation. Concurrently, another effect, length contraction, would have you notice that I’m shrinking increasingly as I accelerate. From my frame of reference, I wouldn’t perceive time slowing down or my stature diminishing, but from your outlook, the closer I get to light speed, the shorter and more ageless I appear.
Herein lies a paradox: if I somehow reached light speed, time would seemingly stop for an outside observer as my height approaches zero. I would cease to exist, along with time and space. Luckily, the laws of physics preclude that scenario. Only massless entities can attain that speed limit: photons, gluons, and gravitational effects. Nothing surpasses light speed through space and time.
Rather than feeling disheartened by the universe’s speed limitations, we should celebrate them. The speed of light carries a crucial consequence: it underpins the whole notion of causality. All physics, and our comprehensive understanding of everything, hinges on the principle that effects always follow causes, never the other way around.
Consider this: as I approach light speed, you observe my time slowing down. It will cease entirely when I attain light speed. Should I exceed light speed, from your perspective, I’d be reversing time. If I transmitted a signal faster than light, a hypothetical message defying physics, you’d receive it before I sent it. Absent a universal speed limit, discerning which events caused which effects would be impossible, rendering the universe largely incomprehensible.
Finally, here’s a thought-provoking notion: if all signals require time to travel, and time progresses variably in frames of reference moving at different speeds, what does simultaneous meaning? If I wink at my reflection, the reflected wink arrives slightly later than my physical action, due to light needing to bounce off my face, towards the mirror, and back into my eyes. If two events simultaneously occurred across the universe, I must ask, “By whose standard?” Depending on the distance separating two locations, event 1 might have occurred first for one observer, while event 2 happened prior to event 1 for another. There is no objective simultaneity, no definitive “same time.” This reality stems solely from light’s finite speed. Fascinating, right?
Neuroscience seems like an unlikely place to find fundamental truths that might apply to everything in the universe. The brain is a special object that does things that few other objects in the universe are expected to be able to do. they recognize. they act. They read magazine articles. Usually they are the exception, not the rule.
Perhaps this is why the free energy principle (FEP) has attracted so much attention. In the early 2000s, what began as a tool to explain cognitive processes such as perception and behavior began to be presented as a “unified brain theory.” FEP was then put forward as the definition of life beyond the brain and, inevitably, as the basis for a new kind of artificial intelligence capable of reasoning. Today, some proponents argue that FEP even encapsulates what it means for something to exist in the universe. “The free energy principle can be read as the physics of self-organization,” says its founder. carl friston At University College London. “It's a description of what lasts.”
But some researchers, frustrated by the changes in scope, are skeptical that the FEP can deliver on many of its loftiest promises. “It was a moving target,” he says Mateo Colomboa philosopher and cognitive scientist at Tilburg University in the Netherlands.
All of this makes FEP a source of both fascination and frustration. While notoriously difficult to understand, its dizzying breadth is key to its enduring appeal. Therefore, given the claim that it can be used to explain…
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