Nuclear Magnetic Resonance
Nuclear Magnetic Resonance (NMR) Lab
Qubits encoded in nuclear spins
Qubits can be encoded in nuclear spins of certain atomic isotopes in molecules. The magnetic states of the nuclear spins can be accessed and manipulated using nuclear magnetic resonance (NMR) techniques. Properly modulated radio frequency fields and pulses of field gradients are used to prepare initial states and control the dynamics of the system in a liquid sample of the molecule of interest (about 1%) diluted in a deuterated solvent. This system can be understood as a quantum molecular simulator or a quantum processor in a tube. We can literally program the dynamics of nuclear spins into molecules containing up to a dozen qubits. The experiments with spin qubits at UFABC employ a 500 MHz NMR spectrometer that operates in the multiuser regime.
The laboratory has infrastructure for preparing fire-sealed isotope samples in 5mm quartz tubes. Own protocols for analysing experimental data to perform state and process tomography, optimisation of pulse sequences, measurements of energy fluctuations, work and heat for experiments in quantum thermodynamics. On this platform we have an extraordinary precision for manipulation and measurement of non-classical states encoded in nuclear spin. These characteristics turn up this the main system used in fundamental experiments in the emerging area known as Quantum Thermodynamics.
Twin Photons Lab
Qubits encoded in single photons
Our lab operates the only source of individual entangled photons in the state of São Paulo. Twin photons, entangled in polarisation, are produced by parametric downward conversion (PDC). The central element of the laboratory's photon source is a non-linear crystal β-Barium-Borate (BBO). A high power UV diode laser with a wavelength of 405 nm (pump laser) is focused on the interface of two BBO crystals. If the polarisation of the pumping beam and the BBO crystal axis are combined to allow conservation of energy and momentum, some of the photons from the pumping are converted into two photons in the near infrared with a wavelength of 810 nm. These converted photons emerge on opposite sides of an emission cone and form a pair of entangled photons in horizontal and vertical polarisation (| H, H> + | V, V>) / sqrt (2).
Temporal displacements of the generated photon wave packets and dispersion effects are compensated for by two crystals of ytterbium vanadate (YVO). The photons produced are coupled in optical fibers and then combined in different applications associated with new quantum technologies.
Squeezed Light Lab
Applications to quantum metrology
Squeezed states of light are characterised when the intensity of the electric field Ԑ (for some phases) has a quantum uncertainty less than that of a coherent state (which describes the light produced by a good laser). The term squeezing refers to reduced quantum uncertainty in one of the field quadrature. To satisfy the Heisenberg uncertainty ratio, a compressed state also has phases in which the uncertainty of the electric field is increased, that is, greater than that of a coherent state.
Squeezed states of light are used to reduce the noise of photon counting (shot noise) in high precision optical measurements, mainly in quantum metrology. By compressing two modes of the electromagnetic field, it is possible to produce shiny entangled states in continuous variables. On this platform, investigations are carried out on these non-classical states of light and applications in new quantum technologies.
Trapped Ions Lab
Qubits encoded in electronic states
Trapped ions systems have been used by companies and research institutes to build prototypes of a scalable quantum computer. On this platform, in an ultra high vacuum environment, atomic ions are confined and suspended in free space through electromagnetic fields. Qubits are encoded in hyper-fine electronic levels of individual ions, and non-classical information (stored in these levels) can be transferred, from one ion to another, through the collective quantised movement of the ions that share the trap (which interact via Coulomb force). Lasers at different frequencies are applied to induce coupling between electronic and vibrational states. Each ion in the trap can be manipulated individually, entanglement and quantum logic gates between different ions can be produced. Initial states of motion can be prepared with the side-band-cooling technique and electronic states are measured with extreme precision. The UFABC trap is in an advanced stage of development and assembly, and should be functional soon. This is the first setup of trapped ions to be operated in Brazil.