  Since the discovery of the first hot Jupiter orbiting a solar-type star, 51
Peg, in 1995, more than 4000 exoplanets have been identified using various
observational techniques. The formation process of these sub-Earths remains
elusive, and acquiring additional samples is essential for investigating this
unique population. In our study, we employ a novel GPU Phase Folding algorithm
combined with a Convolutional Neural Network, termed the GPFC method, on Kepler
photometry data. This method enhances the transit search speed significantly
over the traditional Box-fitting Least Squares method, allowing a complete
search of the known KOI photometry data within hours using a commercial GPU
card. To date, we have identified five promising sub-Earth short-period
candidates: K00446.c, K01821.b, K01522.c, K03404.b, and K04978.b. A closer
analysis reveals the following characteristics: K00446.c orbits a K dwarf on a
0.645091-day period. With a radius of $0.461R_\oplus$, it ranks as the second
smallest USP discovered to date. K01821.b is a sub-Earth with a radius of
$0.648R_\oplus$, orbiting a G dwarf over a 0.91978-day period. It is the second
smallest USP among all confirmed USPs orbiting G dwarfs in the NASA Archive.
K01522.c has a radius of $0.704 R_\oplus$ and completes an orbit around a
Sun-like G dwarf in 0.64672 days; K03404.b, with a radius of $0.738 R_\oplus$,
orbits a G dwarf on a 0.68074-day period; and K04978.b, with its planetary
radius of $0.912 R_\oplus$, orbits a G dwarf, completing an orbit every 0.94197
days. Three of our finds, K01821.b, K01522.c and K03404.b, rank as the smallest
planets among all confirmed USPs orbiting G dwarfs in the Kepler dataset. The
discovery of these small exoplanets underscores the promising capability of the
GPFC method for searching for small, new transiting exoplanets in photometry
data from Kepler, TESS, and future space transit missions.
