Current silicon technology has steadily improved our ability to compute by increasing the number of bits and gates. Now researchers are developing Quantum technology to develop the next generation of computer communication, control, signal processing, and sensors.

Quantum technology (QT) applies quantum mechanical properties such as quantum entanglement, quantum superposition, and No-cloning theorem to quantum systems such as atoms, ions, electrons, photons, or molecules. Quantum bit is the basic unit of quantum information. Whereas in a classical system, a bit is either in one state or the another. However, quantum qubits can exist in large number of states simultaneously, property called Superposition.

Quantum entanglement is a phenomenon where entangled particles can stay connected in the sense that the actions performed on one of the particles affects the other no matter what’s the distance between them. No-cloning theorem tells us that quantum information (qubit) cannot be copied.

There are three key areas of quantum computing, which are quantum information technologies, quantum cryptography, and quantum sensors. Quantum cryptography using no cloning and entanglement principles develops perfectly random keys for unhackable communications. quantum sensing allows high-precision measurements of, for example, magnetic, electric, or gravitational fields, and has applications in areas such as microscopy, medicine, time measurement, and geophysics.

### Quantum and Microelectronics

The success of quantum technologies relies on the recent technological advancements, which enable the controlled creation of individual quantum mechanical systems as well as their direct manipulation and measurement.

Microelectronics plays a crucial role in harnessing quantum technologies as future key technologies. On the one hand, semiconductor processes are an important part of creating quantum technological systems. Above all, however, high-performance electronic chips are needed to control the quantum setups and process the resulting extensive measurement data. Microelectronics thus provides the interface from quantum systems to the outside world. In addition to the performance requirements, some applications require that the systems are cooled to extremely low temperatures. This results in additional requirements for the mechanical structure and for the electrical design of the circuits.

### Chiplets for Quantum technologies

On the other hand, many quantum applications often require highly customized circuits, for example, in terms of the voltage levels they need to process or provide. Furthermore, the data processing requirements are sometimes extremely high, so that only the most modern circuit concepts and circuits can meet them. Often, the electronics must also be fit in the smallest possible installation space, either due to the requirements of the application or because it is located in a cryostatic domain. Therefore, novel design concepts such as chiplets are expected to meet these requirements.

Chiplets make it possible to realize data processing with standard or special processors. Moreover, fast analog-to-digital converters (ADCs) or digital-to-analog converters (DACs) will be available as chiplets. With these converters, it would only be necessary to individually design the components that need to be specially adapted. For example, drivers as chiplets could provide the necessary voltage levels. Special technologies such as silicon-germanium semiconductor technology (SiGe) can also be used for this purpose and integrated as chiplets.

### Quantum and Nanotechnology

Quantum technology and nanotechnology go hand in hand with each other. One of the main principles of nanotechnology is that when a material is within the quantum regime (i.e. less than 100 nm in thickness), it exhibits quantum effects rather than the bulk effects seen with larger molecular structures. Nanoscale systems are ideally suited to study quantum mechanical effects and explore these as resources for emerging quantum technology such as quantum sensing, communication or computing.

Nanotechnology is an application of Quantum physics, in a simple way, it is one of the practical aspects of quantum theory, for example, the development of devices that are small, light, self-contained, use little energy and that will replace larger microelectronic equipment depends on the nature of quantum variance, scientists theorize that single-molecule sensors can be developed and that sophisticated memory storage and neural-like networks can be achieved with a very small number of molecule.

micro- and nanotechnologies are required for the production of qubit chips and systems with a focus on scaling and manufacturing. With the help of production-compatible process technologies, for example for coating and structuring the qubit chips, superconducting quantum circuits can be manufactured in larger quantities. In perspective, this could enable next-generation quantum computers with up to 500 qubits.

The progress seen in nanoscience over the past few decades now enables exquisite control over the nanoscale structures through fabrication and synthesis approaches. Researchers can now tailor quantum mechanical effects at will with high finesse.

Many nanomaterials exhibit quantum properties which can then be utilized for many quantum technology applications, such as quantum computing, quantum electronics and quantum photonics.

### Silicon as Quantum bits

Quantum computers shall bring power of massive parallel processing, equivalent of supercomputer to a single chip. They can consider different possible solutions to a problem simultaneously, quickly converge on the correct solution without check each possibility individually. This dramatically speed up certain calculations, such as number factoring.

Quantum bits, or qubits, are the basic building blocks of quantum computers, just as bits are that of modern computers. The power of quantum computers depends on the number of qubits and their quality measured by coherence, and gate fidelity. Qubit is very fragile, can be disrupted by things like tiny changes in temperature or very slight vibrations. Coherence measures the time during which quantum information is preserved. The gate fidelity uses distance from ideal gate to decide how noisy a quantum gate is.

Researchers around the world have been exploring a range of different physical systems to act as qubits, including Superconducting quantum computing (qubit implemented by the state of small superconducting circuits (Josephson junctions)); Trapped ion quantum computer (qubit implemented by the internal state of trapped ions); Optical lattices (qubit implemented by internal states of neutral atoms trapped in an optical lattice); Quantum dot computer, spin-based (e.g. the Loss-DiVincenzo quantum computer) (qubit given by the spin states of trapped electrons), and Quantum dot computer, spatial-based (qubit given by electron position in double quantum dot.) . Qubits hold great promise, but unlike bits in traditional computing, they are error prone. This means millions are required for complex calculations to allow for error correction.

Recently, however, experimental breakthroughs in silicon-based nanodevices have brought a another option, to manufacture quantum processors in the same way as conventional microprocessors, by leveraging widely deployed industrial complementary metal-oxide-semiconductor (CMOS) technology. Spin qubits highly resemble the semiconductor electronics and transistors as we know them today. They deliver their quantum power by leveraging the spin of a single electron on a silicon device and controlling the movement with tiny, microwave pulses. Electron spins in silicon quantum dots are attractive systems for quantum computing owing to their long coherence times and the promise of rapid scaling of the number of dots in a system using semiconductor fabrication techniques.

**Quantum Electromechanical Systems (QEMS)**

Quantum electromechanical systems (QEMS) are nano-fabricated systems that use a series of transducers operating at the quantum limit. The quantum operation limit creates a highly sensitive system that is usable for both microscopy systems or for detecting the magnetic moment of a single spin.

There are many sub-areas to QEMS, for which there is a different application for the incorporated QEMS. The most common areas of interest are superconducting quantum interference devices (SQUIDs), coherent quantum electronics and single spin magnetic resonance force microscopy.

QEMS operate at a quantum efficiency level when the quantum energy exhibited by the device is greater than the thermal energy. There must also be a simultaneous quality factor that is of the order of 10^{5}. There are both optical and electronic systems that rely on QEMS and are realised by using an oscillator that forms an optical cavity, or moves in motion with an external magnetic field, respectively. However, the oscillator does require GHz frequencies, so there are some limits to the time scales required for moving charge around a small circuit.

### References and Resources also include:

https://semiengineering.com/microelectronics-for-quantum-technologies/