Effective Two-State Model and NOON States for Double-Well Bose-Einstein Condensates in Strong-Interaction Regime

The model of double-well Bose-Einstein condensates in the strong-interaction regime is shown to reduce adiabatically to an effective two-state model describing the Rabi oscillations between the two atomic Fock states ｜N, 0〉 and [0, N〉, and the NOON states of arbitrary ultracold atoms can therefore be generated periodically from the initial state of either one of the Foek states.

Heralded path-entangled NOON states generation from a reconfigurable photonic chip

Maximal multi-photon entangled states,known as NOON states,play an essential role in quantum metrology.With the number of photons growing,NOON states are becoming increasingly powerful and advantageous for obtaining supersensitive and super-resolved measurements.In this paper,we propose a universal scheme for generating three-and four-photon path-entangled NOON states on a reconfigurable photonic chip via photons subtracted from pairs and detected by heralding counters.Our method is postselection free,enabling phase supersensitive measurements and sensing at the Heisenberg limit.Our NOON-state generator allows for integration of quantum light sources as well as practical and portable precision phase-related measurements.

On-chip quantum NOON state sensing for temperature and humidity

A maximal photon number entangled state,namely NOON state,can be adopted for sensing with a quantum enhancedprecision.In this work,we designed silicon quantum photonic chips containing two types of Mach-Zehnder interferometerswherein the two-photon NOON state,sensing element for temperature or humidity,is generated.Compared with classicallight or single photon case,two-photon NOON state sensing shows a solid enhancement in the sensing resolution andprecision.As the first demonstration of on-chip quantum photonic sensing,it reveals the advantages of photonic chips forhigh integration density,small-size,stability for multiple-parameter sensing serviceability.A higher sensing precision isexpected to beat the standard quantum limit with a higher photon number NOON state.

Efficient entanglement concentration for arbitrary less-entangled NOON state assisted by single photons

We put forward two efficient entanglement concentration protocols （ECPs） for arbitrary less-entangled NOON state. Both ECPs only require one pair of less-entangled NOON state and an auxiliary photon. In the first ECR the auxiliary photon is shared by two parties, while in the second ECP, the auxiliary photon is only possessed by one party, which can increase the practical success probability by avoiding the transmission loss and simplify the operations. Moreover, both ECPs can be used repeatedly to get a high success probability. Based on the above features, our two ECPs, especially the second one, may be useful in the quantum information processing.

Magnetic Field Measurement with Heisenberg Limit Based on Solid Spin NOON State

The maximum entangled number state （NOON state） can improve the sensitivity of physical quantity measure- ment to the Heisenberg limit 1/N. In this work, the magnetic field measurement based on the individual solid spin NOON state is investigated. Based on the tunable effective coupling coefficient, we propose a generation scheme of the three-spin NOON state, i.e, the Creenberger-Horne-Zeilinger （CHZ） state, and discussed the mea- surement resolution reduction due to decoherence. It is unnecessary to entangle spins as many as possible when decoherence exists. In practice, defect spins in diamond and alp donors with long coherence time can be applied with current techniques in the nano-scaled high resolution magnetic measurement.

A scheme for demonstration of four-photon de Broglie wavelength

We propose a scheme to effectively generate a four-photon path-entangled number state [the NOON state i.e. 1/√2（｜N,0〉 ＋ ｜0, N〉）] for the demonstration of four-photon de Broglie wavelength. Our scheme rcquires only linear optical elements, photon detectors and post-selections which are all within the reach of current technology.

Two-parameter estimation with three-mode NOON state in a symmetric triple-well potential

We propose a scheme to realize two-parameter estimation via Bose–Einstein condensates confined in a symmetric triple-well potential.The three-mode NOON state is prepared adiabatically as the initial state.The two parameters to be estimated are the phase differences between the wells.The sensitivity of this estimation scheme is studied by comparing quantum and classical Fisher information matrices.As a result,we find an optimal particle number measurement method.Moreover,the precision of this estimation scheme means that the Heisenberg scaling behaves under the optimal measurement.