Simple code to Display Product QR on Product Image Carousel
OPEN THE FILE
catalog/view/theme/YOUR_TEMPLATE/product7product.tpl

SEARCH FOR CODE
<?php foreach ($images as $image) { ?>
<div class="item"><a href="<?php echo $image['popup']; ?>" class="popup-image" data-image="<?php echo $image['popup']; ?>" data-zoom-image="<?php echo $image['popup']; ?>"><img src="<?php echo $image['thumb']; ?>" title="<?php echo $heading_title; ?>" alt="<?php echo $heading_title; ?>" /></a></div>
<?php } ?>

AFTER ADD:

<div class="item"><a href="<?php echo $image['popup']; ?>" class="popup-image" data-image="https://chart.googleapis.com/chart?chs=500x500&cht=qr&chl=<?php echo 'https://'.$_SERVER['HTTP_HOST'].parse_url( $_SERVER['REQUEST_URI'], PHP_URL_PATH ); ?>&choe=UTF-8" data-zoom-image="https://chart.googleapis.com/chart?chs=500x500&cht=qr&chl=<?php echo 'https://'.$_SERVER['HTTP_HOST'].parse_url( $_SERVER['REQUEST_URI'], PHP_URL_PATH ); ?>&choe=UTF-8"><img src="https://chart.googleapis.com/chart?chs=150x150&cht=qr&chl=<?php echo 'https://'.$_SERVER['HTTP_HOST'].parse_url( $_SERVER['REQUEST_URI'], PHP_URL_PATH ); ?>&choe=UTF-8" title="QR Code to recommend this product" /></a></div>

You can match the dimensions with your template.