Quantum Technology CMD Presentation

What are the two main types of devices discussed in quantum technology?

Single-Photon Emitters and Spin Qubits.

What properties do single-photon emitters offer for secure communications?

They offer secure quantum communications for the quantum internet.

What role do spin qubits play in quantum computing?

They are the building blocks of quantum computers and used as quantum sensors.

How are defects created in semiconductors?

By introducing vacancies (removing atoms) and substitutional dopants (replacing atoms with foreign atoms).

What is the significance of the density of states (DOS) in semiconductors?

It describes the energy levels available for electrons and helps in determining the electronic and optical properties of the material.

According to Bohr's model, what is the relationship between energy levels and electron

What are the two main types of devices discussed in quantum technology?

Single-Photon Emitters and Spin Qubits.

What properties do single-photon emitters offer for secure communications?

They offer secure quantum communications for the quantum internet by providing light particles that cannot be clandestinely intercepted.

What role do spin qubits play in quantum computing?

They serve as the fundamental building blocks of quantum computers and are also utilized as high-precision quantum sensors.

How are defects created in semiconductors?

By introducing vacancies (removing atoms from the crystal lattice) and substitutional dopants (replacing host atoms with foreign atoms).

What is the significance of the density of states (DOS) in semiconductors?

It describes the number of energy levels available for electrons at specific intervals, determining the electronic and optical properties of the material.

According to Bohr's model, what is the relationship between energy levels and electron orbits?

Electrons orbit the nucleus in discrete, quantized paths; energy is only emitted or absorbed when an electron transitions from one orbit level (n) to another, following the relation E = h\nu.

What is an "artificial atom" in a semiconductor context?

It refers to localized defect states (like the NV center) that create discrete energy levels within the bandgap, behaving similarly to the isolated energy levels of a gas-phase atom.

Why is a wide bandgap (E_g) important for quantum defect materials?

A large bandgap ensures that the discrete energy levels of the quantum defect are isolated from the valence and conduction bands, preventing thermal noise from destroying the quantum state.

What are the components of a Nitrogen-Vacancy (NV) center in diamond?

It consists of a nitrogen atom substituting for a carbon atom and an adjacent vacancy (a missing carbon atom) in the diamond lattice.

Define T1 and T2 relaxation times for spin qubits.

• T_1 (Longitudinal relaxation): The time it takes for the spin to return to thermal equilibrium (energy relaxation).
• T_2 (Transverse relaxation): The coherence time, or how long the spin maintains its phase information.

How does the Zeeman Effect influence quantum technology?

It describes the splitting of degenerate energy levels by an external magnetic field (B), which allows for the manipulation and measurement of spin states.

What is Hyperfine Coupling?

The magnetic interaction between the electron spin of the defect and the surrounding nuclear spins, which can be used as a memory for quantum information or as a source of decoherence.

How is the state of a spin qubit typically read out optically?

Through Photoluminescence (PL) or Optically Detected Magnetic Resonance (ODMR), where the intensity of emitted light depends on whether the spin is in the '0' or '1' state.

What is the physical distinction between T{1} and T{2} relaxation times?

T{1} (Longitudinal relaxation) is the time for a spin to return to thermal equilibrium through energy loss. T{2} (Transverse relaxation) is the coherence time, measuring how long the spin maintains its quantum phase information.

Why are single-photon emitters considered "secure" for the quantum internet?

They emit light particles that cannot be clandestinely intercepted or copied without being detected, ensuring secure quantum communications.

Explain how the Zeeman Effect is used to control spin qubits.

An external magnetic field (B) is applied to split degenerate energy levels, which allows researchers to distinguish, manipulate, and measure specific spin states.

What is the dual role of Hyperfine Coupling in a quantum defect system?

It facilitates magnetic interaction between electron and nuclear spins; it can be used as a stable "quantum memory" or act as a source of "decoherence" (noise).

Describe the relationship between a wide bandgap (E_{g}) and quantum state stability.

A wide bandgap acts as an insulator that isolates the defect's discrete energy levels from the valence and conduction bands, preventing thermal noise from destroying the quantum state.

How does Optically Detected Magnetic Resonance (ODMR) serve as a readout tool?

It measures the intensity of Photoluminescence (PL); the light intensity varies based on whether the spin qubit is in the '0' or '1' state, providing an optical way to read quantum information.

Define the two types of structural defects used to create quantum states in semiconductors.

1. Vacancies: Created by removing host atoms from the crystal lattice. 2. Substitutional Dopants: Created by replacing host atoms with foreign atoms (e.g., Nitrogen in Diamond).

Why are localized defect states in semiconductors called "artificial atoms"?

Because they create discrete, quantized energy levels within the bandgap that behave like the isolated energy levels found in individual gas-phase atoms.

According to Bohr's model, how do electrons interact with energy during transitions?

Electrons orbit in quantized paths; they only emit or absorb energy when transitioning between levels (n), defined by the frequency relation E = h\nu.