1- Quantum Processing Unit (QPU)
A quantum processing unit (QPU) is a specialized hardware unit that performs information processing using
the fundamental principles of quantum mechanics. It uses quantum bits (qubits) instead of conventional bits
to carry out calculations. Different technologies have been developed for the physical realization of qubits:
1-1 Superconducting Transmon Qubits
Superconducting qubits are usually designed using superconducting circuit elements such as Josephson junctions. These circuits operate at microwave frequencies and the qubit state is defined based on the phase difference or energy levels of the current in the superconducting ring. It is the most widely preferred qubit type in industry today. Gate operations are extremely fast and are manufactured in laboratories with advanced manufacturing technologies. Since these systems require extremely low temperatures in the millikelvin range and are highly sensitive to environmental noise and decoherence, error correction techniques are critical.
1-2 Ion-Trap Qubits
Superconducting qubits are usually designed using superconducting circuit elements such as Josephson junctions. These circuits operate at microwave frequencies and the qubit state is defined based on the phase difference or energy levels of the current in the superconducting ring. It is the most widely preferred qubit type in industry today. Gate operations are extremely fast and are manufactured in laboratories with advanced manufacturing technologies. Since these systems require extremely low temperatures in the millikelvin range and are highly sensitive to environmental noise and decoherence, error correction techniques are critical.
1-3 Photonic Qubits
In photonic qubits, information is encoded in the properties of photons, such as their polarization or phase. Quantum gates are implemented using optical circuits and waveguides. Their potential to operate at room temperature and ease of integration with fiber optic infrastructures offer great advantages for quantum communication. However, the weak interaction of photons with each other necessitates complex optical setups.
1-4 Neutral Atom Qubits
In neutral atom-based quantum systems, information is encoded by keeping the electrically uncharged atoms organized in an optical lattice created using lasers.
By precisely controlling the energy levels of the atoms with laser pulses, quantum operations are performed. Thousands of atoms can be arranged in a regular grid structure and individually controlled. The inherent stability of atoms offers a significant advantage in achieving long-term quantum coherence.
However, the scaling of precision laser systems and optical assemblies poses significant engineering challenges. Furthermore, two-qubit gates, which require fine-tuning of the interactions between two qubits, are still under development.
1-5 NV Center Diamond Qubits
The NV center diamond qubit is a quantum computing technology that exploits the nitrogen-vacancy defect in a diamond crystal to provide stable spin states even at room temperature.
Here, the electron spin of the NV center can be controlled by microwave pulses and read optically with a laser beam. The long integrity times and precise magnetic susceptibility of NV centers provide advantages for quantum sensors and small-scale quantum processors.
1-6 Topological Qubits
Topological qubits is an approach to quantum computing that aims to significantly reduce error rates by preserving quantum information in topological states.
In particular, it utilizes the topological properties of exotic particles such as Majorana fermions to naturally shield quantum states from environmental noise and disturbances.
The main advantage of topological qubits is that they can reduce the need for complex error correction algorithms.
2- Cryostat
In quantum computers, many approaches such as superconducting qubits operate at ultra-low temperatures.
Therefore, special freezer-like cryogenic systems are used to ensure the stability of qubits and maintain their quantum state.
Typically, so-called “dilution refrigerators” are capable of cooling down to millikelvin levels.
3- Control and Readout Electronics
Quantum computers interact with classical electronics to receive and process control signals.
Specialized hardware is required to control (process) qubits using microwave pulses, laser systems, pulses with fast rise times, etc., and to receive data in the readout (measurement) phase.
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