Tomography of the Temporal-Spectral State of Subnatural-Linewidth Single Photons from Atomic Ensembles

Yang, Ce; Gu, Zhenjie; Chen, Peng; Qin, Zhongzhong; Chen, Jiefei; Zhang, Weiping

doi:10.1103/physrevapplied.10.054011

Cited by 19 publications

(11 citation statements)

References 47 publications

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“…1. As an example, we use δ-QM to experimentally measure photonic complex temporal wavefunctions, which has, up to now, not yet been directly measured [22][23][24][25][26][27]. Our experimental results verify that this method is robust and efficient with limited mea- The average power of photon stream is about 10 µW.…”

Section: Introductionsupporting

confidence: 51%

δ -Quench Measurement of a Pure Quantum-State Wave Function

et al. 2019

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Measurement of quantum state wavefunction not only acts as a fundamental part in quantum physics but also plays an important role in developing practical quantum technologies. Conventional quantum state tomography has been widely used to estimate quantum wavefunctions, which, however, requires huge measurement resources exponentially growing with the dimension of state. The recent weak-value-based quantum measurement circumvents this resources issue but relies on an extra pointer space. Here, we propose and demonstrate a simple and direct measurement strategy based on δ-quench probe: By quenching its complex probability amplitude one by one (δ-quench) in the given bases, we can directly obtain the quantum wavefunction by projecting the quenched state onto a post-selection state. As compared to the conventional approaches, it needs only one projection basis. We confirm its power by experimentally measuring photonic complex temporal wavefunctions. This new method is versatile and can find applications in quantum information science and engineering.

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Section: Introductionsupporting

confidence: 51%

δ -Quench Measurement of a Pure Quantum-State Wave Function

et al. 2019

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“…Two major physical mechanisms are used to produce biphotons: the spontaneous parametric down conversion (SPDC) [18][19][20][21][22][23][24][25][26][27][28][29][30] and spontaneous four-wave mixing (SFWM) [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] . The SPDC is employed for nonlinear crystals.…”

Section: Introductionmentioning

confidence: 99%

“…However, the cold-atom SFWM source requires a timing sequence to switch the magneto-optical trap off and on, before and after the biphoton generation. Considering the duty cycle of the timing sequence, the SFWM biphoton source of cold atoms typically has a generation rate in the order of 10 2 pairs/s [37][38][39][40] .…”

Section: Introductionmentioning

confidence: 99%

Room-temperature biphoton source with a spectral brightness near the ultimate limit

Chen,

Hsu,

Huang

et al. 2021

Preprint

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The biphotons, or pairs of time-energy entangled photons, generated from a hot atomic vapor via the process of spontaneous four-wave mixing (SFWM) have the following merits: stable and tunable frequencies as well as linewidth. Such merits are very useful in the applications of long-distance quantum communication. However, the hot-atom SFWM biphoton sources previously had far lower values of generation rate per linewidth, i.e., spectral brightness, as compared with the sources of biphotons generated by the spontaneous parametric down conversion (SPDC) process. Here, we report a hot-atom SFWM source of 960-kHz biphotons with a generation rate of 3.7× 10 5 pairs/s. The high generation rate, together with the narrow linewidth, results in a spectral brightness of 3.8× 10 5 pairs/s/MHz, which is 17 times of the previous best SFWM result and also better than all known SPDC results. The all-copropagating scheme employed in our biphoton source is the key improvement, enabling the achieved spectral brightness to be about one quarter of the ultimate limit. Furthermore, this biphoton source had a signal-to-background ratio (SBR) of 2.7, which violated the Cauchy-Schwartz inequality for classical light by about two-fold. Although an increasing spectral brightness usually leads to a decreasing SBR, our systematic study indicates that both of the present spectral brightness and SBR can be further enhanced. This work demonstrates a significant advancement and provides useful knowledge in the quantum technology using photons.

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“…These methods, however, utilize the nonlinear optical processes of the light under test, which are difficult to observe for weak light at the single-photon level. In recent years, various methods for characterizing the temporal-spectral mode of quantum light have been demonstrated, such as single photons and entangled photon pairs [12][13][14][15][16][17][18][19][20][21][22][23], and some have achieved ultrafast (subpicosecond) time resolution [12,13,16,[19][20][21][22][23]. While these methods differ in the details of their measurement procedures, they have a common procedure to reconstruct the form of the wavefunction: projective measurements for the entire tempo- * ogawak@ist.hokudai.ac.jp ral (or spectral or other basis) wavefunction have to be performed first, and then the measurement data is postprocessed, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Direct measurement of ultrafast temporal wavefunctions

Ogawa,

Okazaki,

Kobayashi

et al. 2021

Preprint

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The large capacity and robustness of information encoding in the temporal mode of photons is important in quantum information processing, in which characterizing temporal quantum states with high usability and time resolution is essential. We propose and demonstrate a direct measurement method of temporal complex wavefunctions for weak light at a single-photon level with subpicosecond time resolution. Our direct measurement is realized by ultrafast metrology of the interference between the light under test and self-generated monochromatic reference light; no external reference light or complicated post-processing algorithms are required. Hence, this method is versatile and potentially widely applicable for temporal state characterization.

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Tomography of the Temporal-Spectral State of Subnatural-Linewidth Single Photons from Atomic Ensembles

Cited by 19 publications

References 47 publications

δ -Quench Measurement of a Pure Quantum-State Wave Function

δ -Quench Measurement of a Pure Quantum-State Wave Function

Room-temperature biphoton source with a spectral brightness near the ultimate limit

Direct measurement of ultrafast temporal wavefunctions

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