However, one needs to know what happens, when the thermal baths are strongly coupled to the machine stronger coupling corresponds to more noise, which may adversely affect the quantum correlations. In the weak-coupling regime, the machine is in weak thermal contact with the thermal reservoirs.
The simplest possible example, that of the two-qubit bridge, is a viable mean to generate stationary entanglement.Ī range of results on quantum thermal machines focuses on the quantum correlations and entanglement present in the machine, as well as the role of quantum information. This situation where the minimal system of two qubits interacting with two baths at temperatures b H and b C was considered in the weak coupling (Markovian) regime. This constitutes a way of generating steady-state entanglement, merely through dissipative interactions with several thermal baths at differing temperatures. The nonequilibrium steady-state of autonomous quantum thermal machines can be entangled.
#Alexei kitaev quantum error correction free
One needs devising ways to counter the effects of noise, and maintain entanglement in a system, such as quantum error correction, dynamical decoupling, and decoherence free subspaces. Yaşar Demirel, Vincent Gerbaud, in Nonequilibrium Thermodynamics (Fourth Edition), 2019 14.10.15 Stationary entanglementĮntanglement is understood to be a fragile property of quantum states, that is one typically expects that noise will destroy the entanglement in a quantum state. Yet, there is a number of other interesting NMR QIP implementations, which have not been discussed here! 6 Some of them are: Experimental quantum error correction, Geometric quantum computation using nuclear magnetic resonance, Experimental realization of quantum games on a quantum computer, Experimental implementation of an adiabatic quantum optimization algorithm, Experimental implementation of the quantum Baker’s map, Quantum phase transition of ground-state entanglement in a Heisenberg spin chain simulated in an NMR quantum computer, Simulated quantum computation of molecular energies, Experimental implementation of heat-bath algorithmic cooling using solid-state nuclear magnetic resonance, Characterization of quantum algorithms by quantum process tomography using quadrupolar spins in solid-state nuclear magnetic resonance and Quantum metrology, Nuclear magnetic resonance implementation of a quantum clock synchronization algorithm. Unwanted effects, usually due to small hardware imperfections, can be corrected during and after the a protocol implementation. The power of the technique lies in the precise control over the radiofrequency pulses that implement the quantum logic gates, allowing the manipulation of the coherences and energy level populations. One of the carbon nuclei was used as the ancilla qubit, whereas the other carbon nucleus and hydrogen were in the quantum state, whose Wigner function was measured.įrom the examples presented in this chapter, one can see the extraordinary achievement of NMR QIP. The experiments were carried out using the three qubit of the trichloroethylene molecule, dissolved in chloroform. Which is a particularly useful expression, since it can be directly associated to the scattering circuit. The results are in excellent agreement with the theory, as can be seen from the calculations shown on Chapter 3. Each point ( p, q) in phase space must be determined by a specific pulse sequence. They used the two carbons and the hydrogen nuclei of trichloroethylene as qubits. The experimental result is shown in Figure 5.16, for each state of the computational basis of two qubits. The authors tailored U such as the measurement of 〈 σ z〉 yields the Wigner function W( q, p) = 〈 σ z〉/2 N, where N is the dimension of the Hilbert space.
On the opposite, the knowledge of U brings information about ρ (tomography). Therefore, if ρ is a known state, the measurement of 〈 σ z〉 brings information about the operator U (spectroscopy). By measuring the output state of the probe, we obtain 〈 σ z〉, which connects to the input state ρ and the conditional transformation U through the expression: 〈 σ z〉 = Re. A probe qubit enters the upper line of the circuit and a generic multi-qubit state ρ enters the lower line. The generic “scattering” circuit is shown in Figure 5.15.
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