Quantum Worlds and Cosmic Frontiers
Quantum Worlds and Cosmic Frontiers
In classical physics, particles like electrons were thought to have definite positions and velocities at all times. Quantum mechanics shattered that view. Today we say an electron’s state is described by a wave function, a complex probability cloud, not a point particle. This wave function evolves smoothly (following the Schrödinger equation) until a measurement is made. When unobserved, an electron’s position is spread out as a probability wave. But the instant we measure it, the wave function “collapses” to a single result. In other words, quantum theory only predicts probabilities until you look – and then you see a definite outcome. This is the essence of the measurement problem: quantum superpositions produce only one observed result, a process that still puzzles physicists.
Key features of the quantum description include:
Wave–Particle Duality: Quantum objects (photons, electrons, etc.) exhibit either wave-like or particle-like behavior depending on the experiment. In practice, when not observed they act like waves (hence the wave function), but measurements yield particle-like hits.
Superposition: An electron can be in a combination of states simultaneously (e.g. “spin up and spin down”) until measured. Only upon measurement does one outcome emerge.
Quantization: Some properties (like angular momentum or energy) come in discrete steps. The Stern–Gerlach experiment shows that an electron’s spin along any axis is always found as exactly “up” or “down” – never in between.
Uncertainty Principle: Crucial pairs of properties (such as position and momentum) cannot both be known exactly. Any attempt to pin down one disturbs the other. In plain terms: the more precisely you measure an electron’s location, the less you know about its motion, and vice versa.
Entanglement: Two or more particles can share one joint quantum state, no matter how far apart they are. Measuring one instantly influences the state of the other(s). This non-classical linkage underpins much of quantum technology (and even has been called “spooky action at a distance”).
These concepts underpin why a single electron in, say, an atom, cannot be assigned a fixed trajectory or position before measurement. Instead it’s described by a wavefunction that gives a probability distribution over space. When we do measure it, we pick out one point – but that choice is fundamentally random (subject only to the probabilities given by |ψ|²) and causes the collapse of the wave function. In Schrödinger’s famous cat thought-experiment, the cat is effectively both alive and dead (a superposition) until we open the box, when only one outcome is observed. All of these bizarre effects show that at the quantum level our classical intuition breaks down.
Spin Measurements and the Stern–Gerlach Experiment
A concrete illustration of quantum weirdness comes from measuring electron spin. In the Stern–Gerlach experiment, a beam of atoms (each carrying an electron) passes through a strong magnetic field. Classically we’d expect the electrons’ magnetic moments to point in all directions, producing a continuous spread of deflections. Instead, the atoms split into two discrete spots on the detector – corresponding to “spin up” or “spin down” along the magnetic field axis. In other words, the spin is quantized.
Even more astonishingly, once we have “prepared” a spin in one direction, we can predict repeated measurements only if we measure that same component again. For example, after measuring an electron to be “spin-up” along the vertical (z) axis, any subsequent measurement along z will again give “up” 100% of the time (the state is now locked in). But if instead we immediately measure the spin along a perpendicular direction (say the horizontal x-axis), the outcome is totally unpredictable – we get “left” or “right” with 50/50 probability. Even though the electron’s original z-spin was known, that information is erased by measuring the x-spin. If we then send it through a z-oriented magnet again, it will not always come out spin-up. The prior x-measurement has “reset” the system, and now it has only a 50/50 chance of up or down along z. This dramatic effect – one measurement disrupting another mutually incompatible one – highlights that quantum measurements fundamentally alter the system (they do not merely reveal a pre-existing hidden value). In short, you can’t measure two orthogonal spin components simultaneously without disturbance; observing one axis completely disturbs the perpendicular axis.
Quantum Computing: Harnessing Superposition and Entanglement
Quantum physics doesn’t just lead to thought experiments – it also enables powerful technology. Quantum computers use qubits (quantum bits) that can be in superpositions of 0 and 1 simultaneously, and they exploit entanglement to process many possibilities at once. Thanks to these features, quantum computers can explore vast computational “branches” in parallel. As Microsoft’s quantum team explains, entanglement and superposition let a quantum computer perform multiple calculations simultaneously – something a classical computer cannot do.
Remarkably, Google’s latest 105-qubit processor, nicknamed Willow, recently demonstrated this power. Willow solved a standard quantum benchmark problem in about five minutes – a task that today’s fastest supercomputer would need on the order of 10^25 years to complete. In other words, a classical computer would take “10 septillion years” to do what Willow did in minutes. In achieving this, Willow passed the coveted “error correction threshold” first proposed by Peter Shor in 1995: as more qubits are added, the error rate in computations actually drops exponentially. This is a critical milestone for scalable quantum computing.
Figure: Google’s new 105-qubit “Willow” quantum processor. By encoding logical qubits across many physical qubits, Willow achieves error rates that shrink as the system grows, unlocking powerful computations beyond classical reach.
Google’s blog on Willow makes a bold claim: this “mind-boggling” performance even “lends credence to the notion that quantum computation occurs in many parallel universes, in line with the idea that we live in a multiverse” – a concept first proposed by physicist David Deutsch. In other words, the idea is that each qubit explores multiple outcomes “at once” across a vast quantum reality. Some researchers take this as philosophical support for the Many-Worlds interpretation of quantum mechanics or even a sort of cosmic “simulation” hypothesis (the notion our universe is like a computer simulation). However, others caution that the same results can be fully explained by standard quantum math (wavefunctions and collapse) without invoking literal alternate worlds. In practice, what matters today is that the unique behaviors of qubits – superposition, entanglement, coherence – do confer a huge speedup for certain problems. Even if the role of parallel universes remains hotly debated, companies like Google and IBM are focused on the practical improvements: longer qubit coherence, better chip designs, and clever error-correction techniques to make quantum machines more powerful and reliable.
The Universe on Grand Scales
If quantum mechanics is mind-bending at the smallest scales, the cosmos is equally staggering at the largest scales. Observations by the Hubble Space Telescope and other surveys show that the observable universe is about 93 billion light-years across. That means light has traveled some 46.5 billion light-years from us in every direction. Within this vast sphere lie on the order of two trillion galaxies – a number far larger than we once thought. Many of these galaxies are faint and remote (indeed, about 90% are too dim for us to see without deep observations). Each galaxy contains billions to trillions of stars, which in turn host even more planets. Even our own Milky Way is enormous: it spans over 100,000 light-years and contains roughly 200–400 billion stars. Our solar system sits about 26,000 light-years from the galactic center, and together we orbit that center. In fact, we’re moving through space at astonishing speed – about 515,000 miles per hour (828,000 km/h) around the galaxy – yet we barely notice it because motion is relative.
Figure: A small patch of sky imaged by Hubble in the Hubble Deep Field. Nearly 10,000 galaxies are visible in this single frame. Extrapolating such observations suggests our observable universe contains on the order of 2 trillion galaxies. Each galaxy contains billions of stars. These mind-boggling numbers highlight the enormous scale of the cosmos.
This immense scale sets the stage for speculative ideas. Quantum theory itself contains deep uncertainties (Heisenberg’s principle) and the “branching” of possible outcomes (as in the Many-Worlds view). Some have suggested that if spacetime can fluctuate at the quantum level, it might even spawn entirely new regions or “baby universes” under extreme conditions. While such hypotheses blur the line between physics and philosophy, the union of quantum mechanics and cosmology certainly pushes the imagination.
In summary, modern physics reveals a world far different from everyday intuition. At tiny scales, particles behave like waves of probability and only become definite when observed. At cosmic scales, vast distances and unimaginable numbers of stars overwhelm the imagination. Quantum technologies like the Willow chip are now turning these strange quantum laws into real advantages, hinting at deeper truths (and maybe parallel worlds) along the way. As we probe both the smallest particles and the largest structures, we continue to discover that reality is profoundly and beautifully complex, governed by rules that go beyond classical common sense.
Sources: Reputable sources including NASA, Science, and major news outlets (e.g. Google’s Quantum AI blog; Live Science on Willow; The Guardian on galaxies), as well as scientific references (Wikipedia entries on the wave function, Stern–Gerlach experiment, etc.). These sources support the above discussion of quantum principles and cosmic scales. All quoted figures and facts are cited accordingly.
Citations
en.wikipedia.org
Wave function - Wikipedia
In quantum physics , a wave function (or wavefunction) is a mathematical description of the 136 of an isolated quantum system . The most common symbols for a wave function are the Greek letters ψ and Ψ (lower- case and capital 138, respectively). Wave functions are complex- valued . For example, a wave function might assign a complex number to each point in a region of space. The 140[ 1 ][ 2 ][ 3 ] provides the means to turn these complex probability amplitudes into actual probabilities. In one common form, it says that the 142 of a wave function that depends upon position is the probability density of
en.wikipedia.org
Wave function - Wikipedia
point in a region of space. The Born rule [ 1 ][ 2 ][ 3 ] provides the means to turn these complex 141 into actual probabilities. In one common form, it says that the squared modulus of a wave function that depends upon position is the 143 of measuring a particle as being at a given place. The integral of a wavefunction's squared modulus over all the system's degrees of freedom must be equal to 1, a condition called normalization. Since the wave function is
en.wikipedia.org
Measurement problem - Wikipedia
In quantum mechanics, the measurement problem is the problem of definite outcomes: quantum systems have superpositions but quantum measurements only give one definite result.[ 1 ][ 2 ]
en.wikipedia.org
Wave–particle duality - Wikipedia
Wave–particle duality is the concept in quantum mechanics that fundamental entities of the universe, like 230 and electrons , exhibit 232 or wave properties according to the experimental circumstances.[ 1 ]: 59 It expresses the inability of the 234 concepts such as particle or wave to fully describe the behavior of quantum objects.[ 2 ]: III:1-1 During the 19th and early 20th centuries, light was found to behave as a wave then later was discovered to have a particle-like behavior, whereas electrons behaved like particles in early experiments then were later discovered to have wave-like behavior. The concept of duality arose
en.wikipedia.org
Stern–Gerlach experiment - Wikipedia
In quantum physics , the Stern–Gerlach experiment demonstrated that the spatial orientation of 209 is quantized . Thus an 211 system was shown to have intrinsically quantum properties. In the original experiment, silver atoms were sent through a spatially- varying 213, which deflected them before they struck a detector screen, such as a 215. Particles with non-zero magnetic moment were deflected, owing to the magnetic field 217, from a straight path. The screen revealed discrete points of accumulation, rather than a continuous distribution,[ 1 ] owing to their quantized spin. Historically, this experiment was decisive in convincing
plato.stanford.edu
The Uncertainty Principle (Stanford Encyclopedia of Philosophy/Fall 2024 Edition)
> In quantum mechanics, there is no measurement procedure by which one can accurately measure the position of a system without disturbing it momentum, in the sense that some measure of inaccuracy in position and some measure of the disturbance of momentum of the system by the measurement cannot both be arbitrarily small.
quantum.microsoft.com
Microsoft Quantum | Entanglement
Entanglement is a fundamental concept of quantum mechanics that describes a non- classical correlation, or shared quantum state, between two or more quantum systems (or quantum particles) even if they are separated by a large distance. This phenomenon is also known as quantum non-locality, and it is one of the key features of quantum mechanics that distinguishes it from classical mechanics. Quantum systems are described by a mathematical object called a wavefunction, which contains information about the possible outcomes of measurements that can be performed on the systems. When two or more quantum systems are entangled, their wavefunction cannot be expressed as a product of individual wavefunctions for each system. Instead, the systems are described by a single wavefunction
en.wikipedia.org
Measurement problem - Wikipedia
A thought experiment called Schrödinger's cat illustrates the measurement problem. A mechanism is arranged to kill a cat if a quantum event, such as the decay of a radioactive atom, occurs. The mechanism and the cat are enclosed in a chamber so the fate of the cat is unknown until the chamber is opened. Prior to observation, according to quantum mechanics, the atom is in a 74, a linear combination of decayed and intact states. Also according to quantum mechanics, the atom-mechanism–cat composite system is described by superpositions of compound states. Therefore, the cat would be described as in a superposition, a linear combination of two states an "intact atom–alive cat" and a "decayed atom–dead cat". However, when the chamber is
en.wikipedia.org
Stern–Gerlach experiment - Wikipedia
The top illustration shows that when a second, identical, S-G apparatus is placed at the exit of the first apparatus, only z+ is seen in the output of the second apparatus. This result is expected since all particles at this point are expected to have z+ spin, as only the z+ beam from the first apparatus entered the second apparatus.[ 11 ]
en.wikipedia.org
Stern–Gerlach experiment - Wikipedia
The middle system shows what happens when a different S-G apparatus is placed at the exit of the z+ beam resulting of the first apparatus, the second apparatus measuring the deflection of the beams on the x axis instead of the z axis. The second apparatus produces x+ and x- outputs. Now classically we would expect to have one beam with the x characteristic oriented + and the z characteristic oriented +, and another with the x characteristic oriented - and the z characteristic oriented +.[ 11 ]
en.wikipedia.org
Stern–Gerlach experiment - Wikipedia
The bottom system contradicts that expectation. The output of the third apparatus which measures the deflection on the z axis again shows an output of z- as well as z+. Given that the input to the second S-G apparatus consisted only of z+, it can be inferred that a S-G apparatus must be altering the states of the particles that pass through it. This experiment can be interpreted to exhibit the uncertainty principle: since the angular momentum cannot be measured on two perpendicular directions at the same time, the measurement of the angular momentum on the x direction destroys the previous determination of the angular momentum in the z direction. That's why the third apparatus measures renewed z+ and z- beams like the x measurement really made a clean slate of the
en.wikipedia.org
Stern–Gerlach experiment - Wikipedia
The results show that particles possess an intrinsic angular momentum that is closely analogous to the angular momentum of a classically spinning object, but that takes only certain quantized values. Another important result is that only one component of a particle's spin can be measured at one time, meaning that the measurement of the spin along the z-axis destroys information about a particle's spin along the x and y axis.
quantum.microsoft.com
Microsoft Quantum | Entanglement
In quantum computing, entanglement is used to enable quantum parallelism, which is the ability of quantum computers to perform multiple calculations simultaneously. Entanglement allows quantum computers to manipulate many qubits in a single operation, instead of manipulating each qubit individually, as in classical computing. For example, consider two qubits that are initially prepared in an entangled state. If a measurement is made on one of the qubits, and it is found to be in the state |0⟩, then the state of the other qubit immediately collapses to the state |0⟩ as well. Similarly, if the first qubit is measured to be in the state |1⟩, then the state of the second qubit collapses to the state |1⟩ as well.
livescience.com
Google's 'Willow' quantum chip has solved a problem that would have taken the best supercomputer a quadrillion times the age of the universe to crack | Live Science
Google scientists have created a new quantum processor that, in five minutes, cracked a problem that would have taken the world's best supercomputer 10 septillion years to solve. The breakthrough will allow quantum computers to become less error-prone the bigger they get, achieving a milestone that overcomes a decades-long obstacle.
livescience.com
Google's 'Willow' quantum chip has solved a problem that would have taken the best supercomputer a quadrillion times the age of the universe to crack | Live Science
Google says its new quantum processing unit (QPU), dubbed "Willow," is the first in the world to achieve results that are "below threshold" — a milestone outlined by computer scientist Peter Shor in a 1995 paper. The team outlined the technology in a study published Dec. 9 in the journal Nature.
livescience.com
Google's 'Willow' quantum chip has solved a problem that would have taken the best supercomputer a quadrillion times the age of the universe to crack | Live Science
Google's new 105-qubit "Willow" quantum processor has surpassed a key milestone first proposed in 1995 — with errors now reducing exponentially as you scale up quantum computers.
blog.google
Meet Willow, our state-of-the-art quantum chip
the units of computation in quantum computers, have a tendency to rapidly exchange information with their environment, making it difficult to protect the information needed to complete a computation. Typically the more qubits you use, the more errors will occur, and the system becomes classical.
blog.google
Meet Willow, our state-of-the-art quantum chip
Willow’s performance on this benchmark is astonishing: It performed a computation in under five minutes that would take one of today’s fastest supercomputers 10^{25} or 10 septillion years. If you want to write it out, it’s 10,000,000,000,000,000,000,000,000 years. This mind-boggling number exceeds known timescales in physics and vastly exceeds the age of the universe. It lends credence to the notion that quantum computation occurs in many parallel universes, in line with the idea that we live in a multiverse, a prediction first made by David Deutsch.
astronomy.com
How large is the universe? This Week in Astronomy with Dave Eicher
Just how large is the universe? The short answer is 93 billion light-years — at least.
theguardian.com
Universe has 2 trillion galaxies, astronomers say | Astronomy | The Guardian
There are a dizzying 2 trillion galaxies in the universe, up to 20 times more than previously thought, astronomers reported on Thursday. The surprising finding, based on 3D modeling of images collected over 20 years by the Hubble Space Telescope, was published in the Astronomical Journal.
space.com
Milky Way galaxy: Facts about our cosmic neighborhood | Space
Just as Earth orbits the sun, the solar system orbits the center of the Milky Way. Despite hurtling through space at speeds of around 515,000mph (828,000kmph) our solar system takes approximately 250 million years to complete
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