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We report on the second installment of an X-ray monitoring project of sevenluminous radio-quiet quasars (RQQs). New {\sl Chandra} observations of four ofthese, at $4.10\leq z\leq4.35$, yield a total of six X-ray epochs, per source,with temporal baselines of $\sim850-1600$ days in the rest frame. These dataprovide the best X-ray light curves for RQQs at $z>4$, to date, enablingqualitative investigations of the X-ray variability behavior of such sourcesfor the first time. On average, these sources follow the trend of decreasingvariability amplitude with increasing luminosity, and there is no evidence forX-ray variability increasing toward higher redshifts, in contrast with earlierpredictions of potential evolutionary scenarios. An ensemble variabilitystructure function reveals that their variability level remains relatively flatacross $\approx20 - 1000$ days in the rest frame and it is generally lower thanthat of three similarly luminous RQQs at $1.33\leq z\leq 2.74$ over the sametemporal range. We discuss possible explanations for the increased variabilityof the lower-redshift subsample and, in particular, whether higher accretionrates play a leading role. Near-simultaneous optical monitoring of the sourcesat $4.10\leq z\leq 4.35$ indicates that none is variable on $\approx1$-daytimescales, although flux variations of up to $\sim25$\% are observed on$\approx100$-day timescales, typical of RQQs at similar redshifts. Significantoptical-X-ray spectral slope variations observed in two of these sources areconsistent with the levels observed in luminous RQQs and are dominated by X-rayvariations.

Exploratory X-ray Monitoring of Luminous Radio-Quiet Quasars at High Redshift: No Evidence for Evolution in X-ray Variability