how to limit number of post for blog by same author

I have coded as below for Recent post by same author. Code is working fine and giving me recent post by same author, but it show more than one post (but I need 1 post to show)

 <div class="popular-post-wrapper">
                            <h4 class="blog-post-sub-title">Most Recent</h4>
                                <div class="col-md-3 popular-post-thumbnail">
                                    <?php
                                        $query_posts=array(
                                            'orderby' => 'display_name', 
                                            'order' => 'ASC', 
                                            'who' => 'authors',
                                            'posts_per_page' => '1' );
                                        if (have_posts()) : while (have_posts()) : the_post();
                                    ?>

                                    <?php //if ( has_post_thumbnail() ) : ?>
                                    <a href="<?php //the_permalink(); ?>" title="<?php //the_title_attribute(); ?>">
                                    <?php //the_post_thumbnail(); ?>
                                    </a>
                                    <?php //endif; ?> 
                                    <?php if ( has_post_thumbnail() ) {
                                    the_post_thumbnail();
                                    } else { ?>
                                    <img src="https://kubalubra.is/wp-content/uploads/2017/11/default-thumbnail.jpg" alt="<?php the_title(); ?>" />
                                    <?php } ?> 
                                </div>   
                                <div class="col-md-9 post-title-wrapper">
                                   <h3> <a href="<?php the_permalink(); ?>">
                                    <?php the_title();?>
                                    </a></h3>
                                </div>   
                                <?php
                                endwhile; endif;
                                wp_reset_query();
                                ?>
                        </div>