What quantum physics, Quantum physics is the study of matter and energy at the most fundamental level. It aims to uncover the properties and behaviors of nature’s most building blocks.
While many quantum experiments examine very small objects, such as electrons and photons, quantum phenomena are all around us, operating at all scales. However, we may not be able to detect them easily in larger objects. This can give a false impression that quantum phenomena are strange or otherworldly. In fact, quantum science closes the gaps in our knowledge of physics to give us a more complete picture of our everyday lives.
Quantum discoveries have been incorporated into our fundamental understanding of materials, chemistry, biology, and astronomy. These discoveries are a valuable resource for innovation, giving rise to devices such as lasers and transistors, and enabling real breakthroughs in technologies such as quantum computers. Physicists are exploring the potential of quantum science to change our view of gravity and its relationship to space and time. Quantum science can also show how everything in the universe (or in multiple universes) is connected to everything else through higher dimensions that our senses cannot perceive.
The Origins of Quantum Physics
The field of quantum physics arose in the late 1800s and early 1900s from a series of experimental observations of atoms that did not make intuitive sense in classical physics. Among the fundamental discoveries was the realization that matter and energy can be thought of as discrete packets, or quanta, that have a minimum value associated with them. For example, the light of a fixed frequency will deliver energy in quanta called “photons”. At this frequency, each photon will have the same amount of energy, and this energy cannot be broken down into smaller units. In fact, the word “quantum” has Latin roots and means “how much”.
Knowledge of quantum principles changed our understanding of the atom, which consists of a nucleus surrounded by electrons. Early models depicted electrons as particles orbiting the nucleus, much like satellites orbit the Earth. Modern quantum physics instead consider electrons as distributed in orbitals, mathematical descriptions that represent the probability of electrons existing in more than one location within any given range. Electrons can jump from one orbit to another as they gain or lose energy, but they cannot mix between orbits.
Other central concepts helped lay the foundations of quantum physics:
Wave-particle duality: This principle dates back to the early days of quantum science. It describes the results of experiments that show that light and matter have the properties of particles or waves, depending on how they were measured. Today, we understand that these different forms of energy are actually neither particles nor waves. They are separate quantum objects that we cannot easily visualize.
Superposition: This is a term used to describe something as a combination of multiple possible states at the same time. A superposed object is analogous to a wave on the surface of a pond that is the sum of two waves. In a mathematical sense, an object in superposition can be represented by an equation that has more than one solution or result.
Uncertainty Principle: This is a mathematical concept that represents the trade-off between complementary perspectives. In physics, this means that two properties of an object, such as its position and velocity, cannot both be precisely known at the same time. For example, if we accurately measure the position of an electron, we are limited in how accurately we can determine its velocity.
Entanglement: This is a phenomenon that occurs when two or more objects are connected in such a way that they can be considered as a system, even if they are far apart. In this system, the state of one object cannot be fully described without information about the state of another object. Similarly, learning information about one thing automatically tells you something about another and vice versa.
Mathematics and the Probabilistic Nature of Quantum Objects
Because many of the concepts of quantum physics are difficult, if not impossible, for us to visualize, mathematics is essential to the field. Equations are used to describe or predict quantum objects and phenomena in ways that are more accurate than our imaginations.
Mathematics is also necessary to represent the probabilistic nature of quantum phenomena. For example, the position of an electron cannot be known exactly. Instead, it can be defined as being in a range of possible locations (such as within an orbital), with each location associated with the probability of finding an electron there.
Given their probabilistic nature, quantum objects are often described using mathematical “wave functions”, which are solutions to the so-called Schrödinger equation. Waves in water can be characterized by the changing height of the water as the wave passes a fixed point. Similarly, sound waves can be characterized by the changing compression or expansion of air molecules as they pass a point. Wave functions do not track with any physical property in this way. Solutions to wave functions provide probabilities of where an observer might find a particular object in a range of possible options.
However, just as a wave in a pond or a note on a trumpet is spread out and not confined to one place, quantum objects can also be in multiple places and take on different states, as in the case of superposition— Together.
Observation of Quantum Objects
The process of observation in quantum physics is the subject of much debate. Early in the field, scientists were surprised to find that simply observing an experiment affected the outcome. For example, an electron behaved like a wave when not observed, but the process of observing it caused the wave to break up (or, more accurately, “decohere”) and the electron became a particle. Instead of behaving like Scientists now appreciate that the term “observation” is misleading in this context, which suggests that consciousness is involved. Instead, “measurement” better describes the effect, in which the result can change due to the interaction between the quantum phenomenon and the external environment.
This includes the instrument used to measure the trend. Even this relationship has caveats, and requires a thorough understanding of the relationship between measurements and outcomes.