quantum computing · 5 min read

# The Quantum Quest: A Journey to Superposition, Interference and Entanglement

Quantum mechanics is a branch of physics that studies the behavior of subatomic particles, such as electrons, photons and atoms. These particles can exhibit some strange and fascinating phenomena that challenge our common sense and classical intuition. In this article, we will explore three of these phenomena: (1) Superposition: The ability of a quantum particle to exist in a combination of two or more states at the same time, until an observation is made. (2) Interference: The phenomenon where two or more quantum waves can combine to form a new wave with a different amplitude and phase. (3) Entanglement: The phenomenon where two or more quantum particles can share a quantum state and influence each other, even when they are separated by large distances.

Quantum mechanics is a branch of physics that studies the behavior of subatomic particles, such as electrons, photons and atoms. These particles can exhibit some strange and fascinating phenomena that challenge our common sense and classical intuition. In this article, we will explore three of these phenomena: superposition, interference and entanglement.

## Superposition

Superposition is the ability of a quantum particle to exist in multiple states simultaneously. For example, a photon of light can be both horizontally and vertically polarized at the same time, until we measure it and find out its definite polarization. This means that a quantum particle can have degrees of one-ness and zero-ness, unlike a classical bit that can only be either one or zero. Superposition allows us to encode more information in a single quantum bit (qubit) than in a classical bit.

Superposition also enables quantum parallelism, which is the ability to perform multiple computations at once using a single quantum state. For example, if we have two qubits in superposition, we can apply a function to them and obtain four possible outcomes at once. This is because each qubit can be in two possible states, and the combination of two qubits can be in four possible states. By contrast, a classical computer would need to perform four separate computations to obtain the same results.

Superposition is essential for quantum algorithms, such as Shor’s algorithm for factoring large numbers, Grover’s algorithm for searching unsorted databases, and Deutsch-Jozsa algorithm for determining whether a function is constant or balanced. These algorithms exploit the power of superposition to achieve exponential speedups over classical algorithms.

## Interference

Interference is the phenomenon where two or more quantum particles interact with each other and influence their probabilities of being in certain states. For example, when two photons are sent through a beam splitter, they can interfere constructively or destructively, depending on their relative phases. This means that the outcome of a quantum measurement can depend on the interference pattern of the quantum particles involved.

Interference also enables quantum interference fringes, which are patterns of light and dark bands that result from the superposition of two or more coherent light sources. For example, when we shine a laser through two slits onto a screen, we observe an interference fringe pattern on the screen. This is because each slit acts as a source of light waves that interfere with each other on the screen.

Interference is essential for quantum metrology, which is the science of measuring physical quantities with high precision using quantum resources. For example, we can use interference fringes to measure small distances, angles, velocities and forces with greater accuracy than classical methods. We can also use interference to create quantum sensors and detectors that are more sensitive and robust than classical ones.

## Entanglement

Entanglement is the phenomenon where two or more quantum particles share a quantum state and become inseparable, even when they are far apart. For example, when two photons are generated by a laser and pass through a crystal, they can become entangled in their polarizations. This means that measuring one photon will instantly reveal the polarization of the other photon, no matter how far they are separated. Entanglement creates a quantum correlation that cannot be explained by classical physics.

Entanglement also enables quantum teleportation, which is the process of transferring the quantum state of one particle to another distant particle without sending any physical information. For example, if Alice and Bob share an entangled pair of photons, Alice can teleport the state of her photon to Bob’s photon by performing a joint measurement on her photon and another photon that she wants to teleport. Then she can send the measurement result to Bob via a classical channel, and Bob can apply a unitary operation on his photon to recover the teleported state.

Entanglement is essential for quantum cryptography, which is the science of secure communication using quantum resources. For example, we can use entanglement to create quantum key distribution protocols that allow two parties to share a secret key that is immune to eavesdropping attacks. We can also use entanglement to create quantum secret sharing schemes that allow multiple parties to share a secret among themselves without trusting each other.

## Conclusion

These three phenomena are essential for the development of quantum computing, which is a new paradigm of computation that uses qubits instead of bits to perform operations. Quantum computing has the potential to solve some problems that are intractable for classical computers, such as factoring large numbers, simulating complex systems and optimizing hard problems. However, quantum computing also faces some challenges, such as maintaining coherence, avoiding decoherence and scaling up qubits.

The quantum quest is an ongoing journey to understand and harness the power of superposition, interference and entanglement. It is a journey that requires creativity, curiosity and courage. It is a journey that promises to reveal new insights into the nature of reality and the possibilities of computation.