Quantum information science promises transformative impact over a range of key technologies in computing, communication, and sensing. A prominent example uses entangled photons to overcome the resolution-degrading effects of dispersion in the medical-imaging technology, optical coherence tomography. The quantum solution introduces new challenges: inherently low signal and artifacts, additional unwanted signal features. It has recently been shown that entanglement is not a requirement for automatic dispersion cancellation. Such classical techniques could solve the low-signal problem, however they all still suffer from artifacts. Here, we introduce a method of chirped-pulse interferometry based on shaped laser pulses, and use it to produce artifact-free, high-resolution, dispersion-cancelled images of the internal structure of a biological sample. Our work fulfills one of the promises of quantum technologies: automatic-dispersion-cancellation interferometry in biomedical imaging. It also shows how subtle differences between a quantum technique and its classical analogue may have unforeseen, yet beneficial, consequences.
Energy-time entangled photon pairs remain tightly correlated in time when the photons are passed through equal magnitude, but opposite in sign, dispersion. A recent experimental demonstration has observed this effect on ultrafast time scales using second-harmonic generation of the photon pairs. However, the experimental signature of this effect does not require energy-time entanglement. Here, we demonstrate a direct analogue to this effect in narrow-band second-harmonic generation of a pair of classical laser pulses under similar conditions. Perfect cancellation is observed for fs pulses with dispersion as large as 850 fs 2 , comparable to the quantum result, but with an 10 13 -fold improvement in signal brightness.
Noise poses a challenge for any real-world implementation in quantum information science. The theory of quantum error correction deals with this problem via methods to encode and recover quantum information in a way that is resilient against that noise. Unitarily correctable codes are an error correction technique wherein a single unitary recovery operation is applied without the need for an ancilla Hilbert space. Here, we present the first optical implementation of a nontrivial unitarily correctable code for a noisy quantum channel with no decoherence-free subspaces or noiseless subsystems. We show that recovery of our initial states is achieved with high fidelity (≥ 0.97), quantitatively proving the efficacy of this unitarily correctable code.
This work presents a robust method for whole chip temperature mapping in microfluidic devices using a photostable fluorescent-polymer thin film that can be incorporated during the bonding stage.Temperature measurements are based on the ratio of two bands in the fluorescence spectrum of N,N-bis(2,5-di-tertbutylphenyl)-3,4,9,10-perylenedi carboximide (BTBP) dye. Spectral bands were carefully chosen to minimize errors caused by photobleaching of the dye which results in a perceived drift in the temperature with time. The improvements result in a useful working time for this type of measurement to >20 h. We achieve a temperature resolution ,2 uC with drift less than 0.58 uC h 21 in thin-films of common polymers used in microfluidic device fabrication (polystyrene, polydimethylsiloxane, and polymethylmethacrylate) Finally, we demonstrate the usefulness of this technique by presenting examples of temperature fields mapped by the thin-films in several thermal microfluidic devices.
Optical coherence tomography (OCT) is a non-invasive imaging technology based on low-coherence interferometry that is rapidly finding novel applications in biological sciences and medicine, particularly in disease detection, since it allows high-resolution depth profiles of the samples under consideration [1]. However, material dispersion is a major problem in OCT since it both reduces contrast and resolution with increasing sample depths, hence drastically limiting its potential range of applications.Exciting developments in quantum interferometry have led to the proposal and demonstration of quantum optical coherence tomography (Q-OCT) [2]. This technique relies on Hong-Ou-Mandel (HOM) interferometry which utilizes frequency-entangled photon pairs. The most important advantage of this technique is that it automatically cancels the most pronounced type of dispersion. In addition, it is insensitive to phase fluctuations and unbalanced photon loss in the interferometer, and has a better resolution than OCT. However, entangled photon pairs are difficult to create, manipulate and detect and this has restricted Q-OCT to basic proof-of principle demonstrations in specialized laboratories.Here we report on a completely classical technique based on the time-reversal symmetry of quantum mechanics that achieves all the advantages of HOM interferometry by using oppositely-chirped laser pulses [3]. Since our technique relies on classical lasers instead of entangled photons, it achieves these features with millions of times larger signal -making it an attractive candidate for dispersion-free OCT [4]. In particular, the visibility and width of the CPI interferogram is insensitive to dispersion and photon loss, and inherently robust against phase-fluctuations. Further, we achieve higher resolution than classical interferometers using the same bandwidth. On a fundamental level, our work emphasizes the importance of delineating truly quantum effects from those with classical analogues, and shows how insights gained from quantum mechanics can inspire novel classical technologies.In this talk I will introduce the technique of Chirped-pulse interferometry (CPI), demonstrate its advantageous properties and show how this technique might be suitable for practical bio-medical imaging.
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