# Quantum Computing Technology

**- Overview**

Quantum computing is an emerging technology based on quantum theory in physics. It explains the behavior of particles at the subatomic level and points out that these particles can exist in different positions at the same time. General computer operations store information with 1 and 0, while quantum Computers are not limited by the binary nature of current data processing, so they can provide exponential computing power.

Quantum computing is a new technology that uses quantum entanglement and superposition phenomena to process data, and its computing speed is thousands of times faster than supercomputers, but as a field, it has been stuck in the "very cool but not very practical" stage for many years.

**- Quantum and **Quantum Theory

Very small particles and light behave differently than objects we encounter in normal life, which are described by classical mechanics and classical electrodynamics. Quantum theory describes the mechanics of light and matter at the atomic and subatomic scales, and it forms the fundamental principles of chemistry and much of physics. In its first century of existence, quantum theory has ushered in the information age with its disruptive transistors, lasers, nuclear energy and superconductivity.

In physics, a quantum is the smallest quantity of any physical entity (physical property) involved in an interaction. The basic concept that physical properties can be "quantified" is called the "quantification hypothesis". This means that the magnitude of a physical property can only take discrete values consisting of integer multiples of a quantum.

For example, a photon is a single quantum of light (or any other form of electromagnetic radiation). Similarly, the energy of an electron bound within an atom is quantized and can only exist in certain discrete values. (Atoms and matter are generally stable because electrons can only exist in discrete energy levels within atoms.) Quantization is one of the foundations of the broader physics of quantum mechanics. The quantification of energy and its effect on the interaction of energy and matter (quantum electrodynamics) is part of the fundamental framework for understanding and describing nature.

### - Quantum Technology

Quantum technology is a class of technology that works by using the principles of quantum mechanics (the physics of sub-atomic particles), including quantum entanglement and quantum superposition. You don’t need to know exactly what quantum technology is to make use of it. Your smartphone is a type of quantum technology -- its semiconductors use quantum physics to work – but neither you or the engineer who designed it need to know the ins and outs of quantum mechanics.

Quantum technology promises improvements to a vast range of everyday gadgets, including:

- more reliable navigation and timing systems
- more secure communications
- more accurate healthcare imaging through quantum sensing
- more powerful computing.

**- Quantum Entanglement**

Quantum entanglement is when two atoms are connected, or entangled, despite being separated. If you change the properties of one of them, the other changes instantly. In theory, this would be the case even if the entire universe separates the entangled atoms. If that wasn’t spectacular enough, quantum mechanics says simply observing an atom changes its properties.

One possibility this creates is in enhancing the security of communication through quantum protected cipher keys. You can use entangled atoms to detect whether someone has interfered with the transmission of data.

For example, you can have two entangled atoms with clockwise and anticlockwise ‘spins’. One atom is sent with the encryption key and if an eavesdropper intercepts the transmission, this causes a change in the ‘spin’ of the atom, affecting the overall quantum state of the system and resulting in the detection of the eavesdropping attempt.

**- Quantum Supremacy**

In October 2019, Google researchers announced to much fanfare that their embryonic quantum computer had solved a problem that would overwhelm the dawn of the best supercomputer era. Some say this milestone, known as quantum supremacy, marks quantum computing.

The goal of quantum computing is to provide a fast, secure connection that can instantly send packets of quantum information to computers around the world. The beauty of it is that it is uncrackable - a quality that many world leaders consider highly desirable. The promise of quantum computing seems limitless—faster internet searches, lightning-fast financial data analysis, shorter commutes, better weather forecasts, more effective cancer drugs, revolutionary new materials, and more.

Quantum computers could advance science, life-saving drugs, machine learning methods to diagnose disease faster, materials to make more efficient devices and structures, financial strategies to live better in retirement, and algorithms to quickly direct resources such as ambulances . However, so far, most major breakthroughs have occurred in controlled environments, or using questions for which we already know the answers. In any case, reaching quantum supremacy does not mean that quantum computers are actually ready to do anything useful. Researchers have come a long way in developing the algorithms that quantum computers will use. But the device itself still needs more work. Quantum computing could change the world — but for now, its future remains uncertain.

**- Quantum Superposition**

The feature of a quantum system whereby it exists in several separate quantum states at the same time. For example, electrons possess a quantum feature called spin, a type of intrinsic angular momentum. In the presence of a magnetic field, the electron may exist in two possible spin states, usually referred to as spin up and spin down. Each electron, until it is measured, will have a finite chance of being in either state. Only when measured is it observed to be in a specific spin state. In common experience a coin facing up has a definite value: it is a head or a tail. Even if you don’t look at the coin you trust that it must be a head or tail. In quantum experience the situation is more unsettling: material properties of things do not exist until they are measured. Until you “look” (measure the particular property) at the coin, as it were, it has no fixed face up.

Quantum superposition is the theory that sub-atomic particles exist in multiple states simultaneously. It’s the crux of the Schrodinger’s Cat thought experiment - a cat, a flask of poison and a radioactive source are in a sealed box. If a Geiger counter detects radioactivity, it shatters the flask, releasing the poison and killing the cat. Since the radioactivity detection is a statistical process, the cat can be both alive and dead while the box is sealed, with the outcome only confirmed when you open the box and observe the cat to be in one state or the other.

The practical application of this mind-bending version of reality is most obvious in quantum computers. While digital computers store data as bits (the ones and zeros of binary), quantum computers use qubits that exist as a one, zero or both at the same time. This superposition state creates a practically infinite range of possibilities, allowing for incredibly fast simultaneous and parallel calculations.

One of the properties that sets a qubit apart from a classical bit is that it can be in superposition. Superposition is one of the fundamental principles of quantum mechanics. In classical physics, a wave describing a musical tone can be seen as several waves with different frequencies that are added together, superposed. Similarly, a quantum state in superposition can be seen as a linear combination of other distinct quantum states. This quantum state in superposition forms a new valid quantum state.

**- Quantum Fault Tolerance Theorem**

In quantum computing, the threshold theorem (or quantum fault tolerance theorem) states that a quantum computer with a physical error rate below a certain threshold can suppress the logical error rate to arbitrarily low levels by applying a quantum error correction scheme. This suggests that quantum computers can be fault-tolerant, similar to the von Neumann threshold theorem for classical computing.

The key question addressed by the threshold theorem is whether quantum computers can in practice perform long computations without succumbing to noise. Since quantum computers cannot perform gate operations perfectly, some small constant error is unavoidable; hypothetically, this could mean that a quantum computer with imperfect gates can only apply a constant number of gates before the computation is corrupted by noise.

Surprisingly, the quantum threshold theorem shows that, if the error in executing each gate is small enough, arbitrarily long quantum computations can be performed with arbitrarily good precision for only some small overhead in the number of gates. The formal formulation of the threshold theorem depends on the type of error-correcting code and error model considered.

**<More to come ..>**