Quantum computing using single photons and the Zeno effect

Abstract

Abstract:We show that the quantum Zeno effect can be used to implement several quantum logic gates for photonic qubits, including a gate that is similar to the squareroot of SWAP operation. The operation of these devices depends on the fact that photons can behave as if they were non-interacting fermions instead of bosons in the presence of a strong Zeno effect. These results are discussed within the context of several no-go theorems for non-interacting fermions or bosons.

All-optical switching using the quantum Zeno effect and two-photon absorption

“…In a similar way, it can be shown that the electric field at frequency 2 ω inside the resonator and just after the lower input coupling is given by…”

“…Figure 9 shows the ratio of the self two-photon absorption rate S R to the cross two-photon absorption rate 2 R as a function of the difference in the two wavelengths in nm. It can be seen that the self two-photon absorption is a factor of 8 10 − smaller than the intended cross two-photon absorption for wavelength differences of 0.5 nm or more.…”

“…If the input field in waveguide B is subsequently turned on, it will experience no two-photon absorption and it will be strongly coupled into the resonator. For an appropriate value of the coupling coefficient R (critical coupling), nearly all of the incident power at frequency 2 ω will be transferred into waveguide A and travel to the left. Thus the initial intensity in waveguide A can be used to switch the power in waveguide B into one of two output paths, which corresponds to the operation of an all-optical switch.…”

“…We have previously shown [2][3][4] that the quantum Zeno effect can be used to suppress the failure events that would otherwise occur in a controlled-NOT (CNOT) quantum logic gate based on a linear optics approach [5,6]. Other groups [7,8] have shown that Zeno logic gates of this kind may have advantages over a purely linear optical approach, although stringent requirements on the performance of the devices must be met in order to satisfy the error correction threshold for quantum computing.…”

Two-photon absorption by a quantum dot pair

“…Hence implementations of two-photon quantum protocols in integrated solid state device architectures are being enabled. For example, Zeno-type conditional coherent logic down to the single photon level becomes feasible in a monolithic nanoscale system [19][20][21][22] . Furthermore, charge redistribution or removal could be used to tune the lifetime of the optically-induced entangled state or to convert the optical entanglement into a hybrid or pure particle entanglement, resulting in potential quantum memory technology for single and entangled photons 14,[23][24][25][26][27] as well as opening additional paths for spin-photon entanglement 28,29 .…”